(xcalloc): #ifdef-out unused function.
(xrealloc): Remove code to work around deficient versions of realloc.
Now we have an autoconf-enabled replacement version.
(xmalloc): Remove code to work around deficient versions of malloc.
Now we have an autoconf-enabled replacement version.
Change VOID to void.
(xalloc_exit_failure): Renamed extern.
(xalloc_msg_memory_exhausted): New extern.
(xalloc_fail_func): New extern.
(fixup_null_alloc): Use new variables.