Update gnulib to current HEAD.

Update gnulib to current HEAD.

gdb/ChangeLog:

        * gnulib/update-gnulib.sh (GNULIB_COMMIT_SHA1): Set to
        8d5bd1402003bd0153984b138735adf537d960b0.
        * gnulib/aclocal.m4, configure, config.in: Regenerate.
        * gnulib/import/m4/extern-inline.m4: Import.
        * gnulib/import/wctype-h.c: Import.
        * gnulib/import/Makefile.am: Update.
        * gnulib/import/Makefile.in: Update.
        * gnulib/import/alloca.in.h: Update.
        * gnulib/import/extra/snippet/warn-on-use.h: Update.
        * gnulib/import/localcharset.c: Update.
        * gnulib/import/m4/fcntl-o.m4: Update.
        * gnulib/import/m4/gnulib-cache.m4: Update.
        * gnulib/import/m4/gnulib-comp.m4: Update.
        * gnulib/import/m4/wctype_h.m4: Update.
        * gnulib/import/stdbool.in.h: Update.
        * gnulib/import/verify.h: Update.
        * gnulib/import/wctype.in.h: Update.