Remove several warnings reported with W=1 ...

Improved support for W=1 compilation flag by solving missing-prototypes
and old-style-definition warnings.

The libraries are compiling with warnings (which turn into errors with
the Werror flag).

Outside of libraries, some warnings cannot be fixed without heavy
structural changes.

Change-Id: I1668cf99123ac4195c2a6a1d48945f7a64c67f16
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>

libc: Cleanup remaining files ...

The existing files had some style problems that this patch fixes.

Change-Id: I794e0d96e52f8da0ffa0d70a41f36c4432b4e563
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>