GCC 6.0+ asserts that the memptr argument to the builtin function
posix_memalign is nonnull.
Add the necessary annotation to the prototype and
remove the now unnecessary check to fix a warning.
newlib/Changelog
newlib/libc/include/stdlib.h: Annotate arg to posix_memalign as
non-null.
winsup/cygwin/ChangeLog
malloc_wrapper.cc (posix_memalign): Remove always true nonnull check.
Signed-off-by: Peter Foley <pefoley2@pefoley.com>