manual/memory.texi: Document aligned_alloc.

manual/memory.texi: Document aligned_alloc.

ChangeLog:

2013-12-16  Will Newton  <will.newton@linaro.org>

	* manual/memory.texi (Malloc Examples): Mention aligned_alloc.
	(Aligned Memory Blocks): Add documentation for aligned_alloc
	and suggest it as an alternative to posix_memalign.
	(Hooks for Malloc): Document __memalign_hook is also called
	for aligned_alloc.  (Summary of Malloc): Add summary for
	aligned alloc.  Document __memalign_hook is also called
	for aligned_alloc.