bootstrap: go back to old non-submodule semantics * top/bootstrap-funclib.sh (prepare_GNULIB_SRCDIR): When cloning GNULIB_REFDIR and no submodule 'gnulib' is configured, set the origin’s URL to $gnulib_url and fetch from remote, so that GNULIB_REFDIR is merely an accelerant rather than having different semantics. * build-aux/bootstrap: Regenerate.