indirectly on xalloc. This change causes the openat substitute
to fall back on save_cwd when memory is tight, and for save_cwd to
fail instead of dying when memory is tight, but that's good enough.
+ Problem and initial idea for fix reported by Bastien Roucaries in
+ <http://lists.gnu.org/archive/html/bug-gnulib/2011-01/msg00170.html>.
* lib/openat-proc.c: Include stdlib.h (for malloc), not
xalloc.h (for xmalloc).