platform: add DeepSleepLock ...

RAII object for disabling, then restoring the deep sleep mode

platform: add CriticalSectionLock ...

Critical section class RAII addition

FileSystem: Reintegrated FileSystemLike interface ...

Required for other representations of FileSystems, ie LocalFileSystem

Introduces FileSystemHandle for the same behaviour as FileHandle and
DirHandle.

Requires the following to hook into file/dir lookup:
```
int open(FileHandle **file, const char *filename, int flags)
int open(DirHandle **dir, const char *path)
```

This hook is provided by the FileSystem class, so requires no changes
from implementations.

Add APIs to namespace mbed ...

Certain public APIs are being added to mbed.h so as to make them
part of namespace mebd.

APIs being added are:

	* drivers/UARTSerial.h
	* platform/ATCmdParser.h
	* platform/mbed_poll.h
	* netsocket/nsapi_ppp.h

mbed: version macros are not defined on master ...

Remove mbed OS and mbed 2 version macros. As master can break anytime (should
not break but can happen and shall be expected that there are changes that might affect the bleeding edge developers), there is no remedy for protecting
the sw via macros (either using some special versions, etc). If it is not
defined, means it is developed version of mbed OS/mbed 2 and it is up to a user
to track changes.

Any release of mbed OS 5 and mbed 2 contains these version macros. Thus won't break anything.

Merge pull request #4185 from sarahmarshy/mbed-debug-include ...

Include mbed_debug.h in mbed.h

Set mbed minor and patch version to 0 for master ...

The proper version will be set for releases.

Include mbed_debug.h in mbed.h

Filesystem: Moved retarget related file interfaces into platform

Filesystem: Integrate filesystem classes with common mbed.h entry point

Renamed files in platform to match source names ...

critical.h     -> mbed_critical.h
sleep.h        -> mbed_sleep.h
toolchain.h    -> mbed_toolchain.h
rtc_time.h     -> mbed_rtc_time.h
semihost_api.h -> mbed_semihost_api.h
wait_api.h     -> mbed_wait_api.h

flash: add FlashIAP class ...

Flash IAP that provides erase/read/program to an internal API. It
invokes flash HAL functions.

FlashIAP checks for alignments for erase and program. HAL functions
do not, to avoid duplication per target implementation.

Add a function to transfer control to another app ...

Add the function mbed_start_application() which allows a bootloader to
transfer control to an application.

Platform: Add sleep/deepsleep user facing functions ...

Add sleep/deepsleep functions to platform layer which are replacing HAL
functions with the same name, rename existing symbols in HAL layer
to hal_sleep/hal_deepsleep. This way sleep functions
are always available, even if target doesn't implement them, which makes
the code using sleep clearer. It also enables us to make decision on in
which builds (debug/release) the sleep will be enabled.

Add mbed OS version macros ...

Allow compile-time tests on the version of mbed-os to cope with
e.g. API changes across versions.

To distinguish between mbed OS 2 and mbed OS 5, we use the
MBED_CONF_RTOS_PRESENT macro.

Note: mbed OS 2 versioning is 2.0.MBED_LIBRARY_VERSION

restructure - Added single-nested inc_dir support to legacy build_lib ...

Added single-nested include directories to libraries built with the
legacy build_lib function. Unfortunately, to get this working without
a significant rewrite of the legacy build tools, library header files
are just duplicated in the precompile stage.

For drivers, events, hal, platform, rtos and mbed.h add one level of path to make sure specific and unique includes files are found.

restructure - Reverted move of requirements.txt ...

- Reverted requirements.txt for external dependency in mbed CLI
- Fixed MBED_CONFIG_FILE in paths.py
- Fixed MBED_LIBRARIES in paths.py
- Decreased include namespace for rtos.h

restructure - Fixed include paths damaged by the restructure

restructure - Split hal into drivers+platform+hal ...

hal/common/AnalogIn.cpp -> drivers/AnalogIn.cpp
hal/api/AnalogIn.h -> drivers/AnalogIn.h
hal/api/AnalogOut.h -> drivers/AnalogOut.h
hal/common/BusIn.cpp -> drivers/BusIn.cpp
hal/api/BusIn.h -> drivers/BusIn.h
hal/common/BusInOut.cpp -> drivers/BusInOut.cpp
hal/api/BusInOut.h -> drivers/BusInOut.h
hal/common/BusOut.cpp -> drivers/BusOut.cpp
hal/api/BusOut.h -> drivers/BusOut.h
hal/common/CAN.cpp -> drivers/CAN.cpp
hal/api/CAN.h -> drivers/CAN.h
hal/api/CircularBuffer.h -> drivers/CircularBuffer.h
hal/api/DigitalIn.h -> drivers/DigitalIn.h
hal/api/DigitalInOut.h -> drivers/DigitalInOut.h
hal/api/DigitalOut.h -> drivers/DigitalOut.h
hal/api/DirHandle.h -> drivers/DirHandle.h
hal/common/Ethernet.cpp -> drivers/Ethernet.cpp
hal/api/Ethernet.h -> drivers/Ethernet.h
hal/common/FileBase.cpp -> drivers/FileBase.cpp
hal/api/FileBase.h -> drivers/FileBase.h
hal/api/FileHandle.h -> drivers/FileHandle.h
hal/common/FileLike.cpp -> drivers/FileLike.cpp
hal/api/FileLike.h -> drivers/FileLike.h
hal/common/FilePath.cpp -> drivers/FilePath.cpp
hal/api/FilePath.h -> drivers/FilePath.h
hal/common/FileSystemLike.cpp -> drivers/FileSystemLike.cpp
hal/api/FileSystemLike.h -> drivers/FileSystemLike.h
hal/common/I2C.cpp -> drivers/I2C.cpp
hal/api/I2C.h -> drivers/I2C.h
hal/common/I2CSlave.cpp -> drivers/I2CSlave.cpp
hal/api/I2CSlave.h -> drivers/I2CSlave.h
hal/common/InterruptIn.cpp -> drivers/InterruptIn.cpp
hal/api/InterruptIn.h -> drivers/InterruptIn.h
hal/common/InterruptManager.cpp -> drivers/InterruptManager.cpp
hal/api/InterruptManager.h -> drivers/InterruptManager.h
hal/common/LocalFileSystem.cpp -> drivers/LocalFileSystem.cpp
hal/api/LocalFileSystem.h -> drivers/LocalFileSystem.h
hal/api/LowPowerTicker.h -> drivers/LowPowerTicker.h
hal/api/LowPowerTimeout.h -> drivers/LowPowerTimeout.h
hal/api/LowPowerTimer.h -> drivers/LowPowerTimer.h
hal/api/PortIn.h -> drivers/PortIn.h
hal/api/PortInOut.h -> drivers/PortInOut.h
hal/api/PortOut.h -> drivers/PortOut.h
hal/api/PwmOut.h -> drivers/PwmOut.h
hal/common/RawSerial.cpp -> drivers/RawSerial.cpp
hal/api/RawSerial.h -> drivers/RawSerial.h
hal/common/SPI.cpp -> drivers/SPI.cpp
hal/api/SPI.h -> drivers/SPI.h
hal/common/SPISlave.cpp -> drivers/SPISlave.cpp
hal/api/SPISlave.h -> drivers/SPISlave.h
hal/common/Serial.cpp -> drivers/Serial.cpp
hal/api/Serial.h -> drivers/Serial.h
hal/common/SerialBase.cpp -> drivers/SerialBase.cpp
hal/api/SerialBase.h -> drivers/SerialBase.h
hal/common/Stream.cpp -> drivers/Stream.cpp
hal/api/Stream.h -> drivers/Stream.h
hal/common/Ticker.cpp -> drivers/Ticker.cpp
hal/api/Ticker.h -> drivers/Ticker.h
hal/common/Timeout.cpp -> drivers/Timeout.cpp
hal/api/Timeout.h -> drivers/Timeout.h
hal/common/Timer.cpp -> drivers/Timer.cpp
hal/api/Timer.h -> drivers/Timer.h
hal/common/TimerEvent.cpp -> drivers/TimerEvent.cpp
hal/api/TimerEvent.h -> drivers/TimerEvent.h
hal/api/Transaction.h -> drivers/Transaction.h
hal/api/can_helper.h -> drivers/can_helper.h
hal/.yotta_ignore
hal/CMakeLists.txt
hal/hal/analogin_api.h -> hal/analogin_api.h
hal/hal/analogout_api.h -> hal/analogout_api.h
hal/hal/buffer.h -> hal/buffer.h
hal/hal/can_api.h -> hal/can_api.h
hal/hal/dma_api.h -> hal/dma_api.h
hal/hal/ethernet_api.h -> hal/ethernet_api.h
hal/hal/gpio_api.h -> hal/gpio_api.h
hal/hal/gpio_irq_api.h -> hal/gpio_irq_api.h
hal/hal/i2c_api.h -> hal/i2c_api.h
hal/hal/lp_ticker_api.h -> hal/lp_ticker_api.h
hal/common/mbed_gpio.c -> hal/mbed_gpio.c
hal/common/mbed_lp_ticker_api.c -> hal/mbed_lp_ticker_api.c
hal/common/mbed_pinmap_common.c -> hal/mbed_pinmap_common.c
hal/common/mbed_ticker_api.c -> hal/mbed_ticker_api.c
hal/common/mbed_us_ticker_api.c -> hal/mbed_us_ticker_api.c
hal/module.json
hal/hal/pinmap.h -> hal/pinmap.h
hal/hal/port_api.h -> hal/port_api.h
hal/hal/pwmout_api.h -> hal/pwmout_api.h
hal/hal/rtc_api.h -> hal/rtc_api.h
hal/hal/serial_api.h -> hal/serial_api.h
hal/hal/sleep_api.h -> hal/sleep_api.h
hal/hal/spi_api.h -> hal/spi_api.h
hal/hal/storage_abstraction/Driver_Common.h -> hal/storage_abstraction/Driver_Common.h
hal/hal/storage_abstraction/Driver_Storage.h -> hal/storage_abstraction/Driver_Storage.h
hal/hal/ticker_api.h -> hal/ticker_api.h
hal/hal/trng_api.h -> hal/trng_api.h
hal/hal/us_ticker_api.h -> hal/us_ticker_api.h
hal/api/mbed.h -> mbed.h
hal/api/CThunk.h -> platform/CThunk.h
hal/common/CallChain.cpp -> platform/CallChain.cpp
hal/api/CallChain.h -> platform/CallChain.h
hal/api/Callback.h -> platform/Callback.h
hal/api/FunctionPointer.h -> platform/FunctionPointer.h
hal/api/PlatformMutex.h -> platform/PlatformMutex.h
hal/api/SingletonPtr.h -> platform/SingletonPtr.h
hal/api/critical.h -> platform/critical.h
hal/common/mbed_alloc_wrappers.cpp -> platform/mbed_alloc_wrappers.cpp
hal/common/mbed_assert.c -> platform/mbed_assert.c
hal/api/mbed_assert.h -> platform/mbed_assert.h
hal/common/mbed_board.c -> platform/mbed_board.c
hal/common/mbed_critical.c -> platform/mbed_critical.c
hal/api/mbed_debug.h -> platform/mbed_debug.h
hal/common/mbed_error.c -> platform/mbed_error.c
hal/api/mbed_error.h -> platform/mbed_error.h
hal/common/mbed_interface.c -> platform/mbed_interface.c
hal/api/mbed_interface.h -> platform/mbed_interface.h
hal/common/mbed_mem_trace.c -> platform/mbed_mem_trace.c
hal/api/mbed_mem_trace.h -> platform/mbed_mem_trace.h
hal/common/mbed_rtc_time.cpp -> platform/mbed_rtc_time.cpp
hal/common/mbed_semihost_api.c -> platform/mbed_semihost_api.c
hal/api/mbed_stats.h -> platform/mbed_stats.h
hal/common/mbed_wait_api_no_rtos.c -> platform/mbed_wait_api_no_rtos.c
hal/common/mbed_wait_api_rtos.cpp -> platform/mbed_wait_api_rtos.cpp
hal/api/platform.h -> platform/platform.h
hal/common/retarget.cpp -> platform/retarget.cpp
hal/api/rtc_time.h -> platform/rtc_time.h
hal/api/semihost_api.h -> platform/semihost_api.h
hal/api/toolchain.h -> platform/toolchain.h
hal/api/wait_api.h -> platform/wait_api.h