Previously, fiptool only understood a fixed set of images as
specified in tbbr_config.c.  It preserved unknown images during
the update, unpack and remove operations but it was not possible to
explicitly refer to one of those unknown images.

Add a new --blob option to create/update/unpack/remove images that
are not known at compile time.  This is accomplished by specifying
the UUID and filename pair as shown below:

$ ./fiptool create --blob uuid=01234567-89ab-cdef-0123-456789abcdef,file=foo.bin fip.bin
$ ./fiptool info fip.bin
01234567-89ab-cdef-0123-456789abcdef: offset=0x60, size=0x1AA68

Fixes ARM-software/tf-issues#420

Change-Id: Iaac2504b9a4252289c09e73d29645cbe240f3a82
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

This include provides nothing useful for TF and prevents building
the fiptool using musl libc[0].

[0] https://www.musl-libc.org/

Change-Id: Ied35e16b9ea2b40213433f2a8185dddc59077884
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

* Move stdlib header files from include/stdlib to include/lib/stdlib for
  consistency with other library headers.
* Fix checkpatch paths to continue excluding stdlib files.
* Create stdlib.mk to define the stdlib source files and include directories.
* Include stdlib.mk from the top level Makefile.
* Update stdlib header path in the fip_create Makefile.
* Update porting-guide.md with the new paths.

Change-Id: Ia92c2dc572e9efb54a783e306b5ceb2ce24d27fa