IAR heap stats added

Merge pull request #4949 from theotherjimmy/feature-armc5+armc6 ...

NEW TOOLCHAIN: Add the ARMC6 Compiler

Update mbed 2 discriminator

Correct semihosting check for ARMC6

Enable Compiling with ARMC6 across all targets ...

remove duplicate sys.cpp

Update mbed OS to handle ARMC6 requirements

Initial RTX and tools support for Cortex M-23/M-33 devices

Merge pull request #4938 from deepikabhavnani/IAR_fixes ...

Update IAR to version 8

platform: add DeepSleepLock ...

RAII object for disabling, then restoring the deep sleep mode

Sleep HAL: add sleep manager API ...

Sleep manager provides API to lock/unlock deepsleep. This API allows a user to
control deep sleep.

This API should be done via atomic operations (to be IRQ/thread safe).

__IAR_SYSTEMS_ICC__ macro had issues when 7.5 and 8.11 both workbench are installed

Internal members of std::FILE are not available from IAR8.x

__aeabi_read_tp function required for TLS in Dlib

Merge pull request #4962 from 0xc0170/dev_critical_section ...

platform: add CriticalSectionLock

Merge pull request #4954 from c1728p9/fix_isr_clear ...

Fix ISR powerdown in mbed_application.c

platform: add CriticalSectionLock ...

Critical section class RAII addition

Merge pull request #4920 from scartmell-arm/led-error-sequence ...

Modify LED error sequence to be more recognisable

Merge pull request #4831 from fahhem/less_scanf ...

Remove excessive use of printf/scanf in mbed_fdopen/_open

Fix ISR powerdown in mbed_application.c ...

Fix a calculation error in in powerdown_nvic preventing the last
group of 32 interrupts from getting powered down. The ARMv7m reference
manual states "the total number of interrupt lines is up
to (32*(INTLINESNUM+1)).".

Also rename isr_count to isr_groups_32 for clarity, since this is
actually the number of 32 interrupt groups.

Merge pull request #4908 from geky/fs-reformat ...

fs: Add FileSystem::reformat

Merge pull request #4902 from deepikabhavnani/macro_fix ...

Using CMSIS/RTX Exclusive access macro

Unified the LED error pattern for all boards ...

- Removed the patterned LED sequence, all boards now use the 4 fast pulse, 4 slow pulses LED sequence.
  - Changed the LED used from LED_RED to LED1. Only 58/174 targets seem to define LED_RED but they all define LED1.
  - Removed all ERROR_RED and ERROR_PATTERN definitions from targets/targets.json

retarget: Added ENODEV to error codes

Merge pull request #4817 from c1728p9/move_rtx_handlers ...

Move RTX error handlers into RTX handler file

Using CMSIS/RTX Exclusive access macro

Remove null byte at the end of fdopen's faux filename

Modify LED error sequence to be more recognisable ...

The current error sequence for microcontrollers with less than 4 LEDs is
to toggle an LED at a fixed rate. Change the sequence to 4 short pulses
followed by 4 long pulses.

[M487] Support NuMaker-PFM-M487 board

Use MBED_STATIC_ASSERT instead of static_assert

Update comments for code review