Remove posix_memalign() checks for an old glibc bug
POSIX_MEMALIGN_WITH_COMPLIANT_ALLOCS was added in https://bugzilla.gnome.org/show_bug.cgi?id=328254 to work around a glibc bug where it wrongly checked the size argument to be a power of two instead of the alignment.
This was fixed in glibc in https://sourceware.org/git/?p=glibc.git;a=commit;h=b2bffca2e3b59dd882039e3b0ab835d127bdaf7a about 16 years ago.