manual/memory.texi: Bring aligned allocation docs up to date.

manual/memory.texi: Bring aligned allocation docs up to date.

The current documentation suggests using memalign and valloc which
are now considered obsolete, so suggest using posix_memalign instead.
Also document the possible error return and errno values for memalign
and posix_memalign and improve documentation of __memalign_hook.

ChangeLog:

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

	* manual/memory.texi (Malloc Examples): Clarify default
	alignment documentation.  Suggest posix_memalign rather
	than memalign or valloc.
	(Aligned Memory Blocks): Remove suggestion to use memalign
	or valloc.  Remove obsolete comment about BSD.
	Document memalign errno values and mark the function obsolete.
	Document posix_memalign returned error codes.  Mark valloc
	as obsolete.  (Hooks for Malloc): __memalign_hook is also
	called for posix_memalign and valloc.
	(Summary of Malloc): Add posix_memalign to function summary.
	__memalign_hook is also called for posix_memalign and valloc.