libc: Introduce cdefs.h, assert.h and strlen.c ...

Change-Id: I76091d52571f1950111c4b1670d5fc3883607715
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

libc: Remove non-Arm files ...

Remove all files that don't have only Arm copyright. This is the first
step to cleanup the C library in this repository. They will be re-added
in the following patches.

Change-Id: I72c40a1620d1df3228fc397ec695d569a20245fd
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Create a library file for libc ...

TF Makefile was linking all the objects files generated for the
c library instead of creating a static library that could be
used in the linking stage.

Change-Id: I721daea097e9b13cbb42c9f8eaa2af8fea0799cf
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>