Revert "skip -gfile: call fnmatch without FNM_FILE_NAME"

This reverts commit 02646a4c561ec88491114b87950cbb827c7d614c.  See:

  https://inbox.sourceware.org/gdb-patches/20260203185528.946918-1-guinevere@redhat.com

This commit introduced a non backward compatible change to how GDB
handled skip files.  Something like:

  skip -gfile dir/*.c

no longer matches every file within 'dir/', but now matches every file
in 'dir/' and within every sub-directory of 'dir/', which might not be
what the user wanted.

The original intention behind the commit is solid, we just need to
find a better implementation.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33872