gnulib: Drop no-abort.patch

gnulib: Drop no-abort.patch

Originally added in commit db7337a3d (grub-core/lib/posix_wrap/stdlib.h
(abort): Removed), this patched out all relevant invocations of abort()
in gnulib. While it was not documented why at the time, testing suggests
that there's no abort() implementation available for gnulib to use.

gnulib's position is that the use of abort() is correct here, since it
happens when input violates a "shall" from POSIX. Additionally, the
code in question is probably not reachable. Since abort() is more
friendly to user-space, they prefer to make no change, so we can just
carry a define instead (suggested by Paul Eggert).

Signed-off-by: Robbie Harwood <rharwood@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>