Integrate libc and dlmalloc to opteesp and sp environments

Replace newlib with libc and dlmalloc components in the optee and sp
environments and implement required interfaces. Using the libc component
also required the following changes:
* Fix duplicate __maybe_unused in compiler.h
* Change external/tf_a/include/cdefs.h to point to new cdefs.h
* Resolve __packed usage issues

Signed-off-by: Imre Kis <imre.kis@arm.com>
Change-Id: Ie798eb426378529b5d84f1708beebe85cd061fb3
14 files changed