Really add it.

m4/m4.m4

@@ -0,0 +1,29 @@
+# Copyright 2000 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+# 02111-1307, USA.
+
+# BISON_PROG_GNU_M4
+# -----------------
+# Check for GNU m4, at least 1.3 (supports frozen files).
+AC_DEFUN([BISON_PROG_GNU_M4],
+[AC_PATH_PROGS(M4, gm4 gnum4 m4, m4)
+AC_CACHE_CHECK(whether m4 supports frozen files, ac_cv_prog_gnu_m4,
+[ac_cv_prog_gnu_m4=no
+if test x"$M4" != x; then
+  case `$M4 --help < /dev/null 2>&1` in
+    *reload-state*) ac_cv_prog_gnu_m4=yes ;;
+  esac
+fi])])