bug#15094: Fix for posix_memalign on Cygwin

[Eli Zaretskii]

> Date: Thu, 15 Aug 2013 12:15:49 -0400
> From: Ken Brown <kbrown@cornell.edu>
> CC: 15094@debbugs.gnu.org
> 
> Thanks for pressing me on this, Eli.  I did of course miss the obvious 
> fact that posix_memalign in gmalloc.c will use memalign as defined in 
> the same file.  I'll revert the change.  I'll also use the opportunity 
> to update some comments elsewhere in the code.

Thanks.

> Sorry for the noise.

No need to apologize: no harm was done.