glob: Fix compilation error when glob.h is not replaced. Reported and fix proposed by Reuben Thomas <rrt@sc3d.org> in <https://lists.gnu.org/archive/html/bug-gnulib/2018-08/msg00096.html>. * lib/glob_pattern_p.c: Include <libc-config.h>. * modules/glob (Depends-on): Add libc-config.