* configure.in (WARNING_CFLAGS): Add -Werror when possible.

(CFLAGS): Do not include the WARNING_CFLAGS here, since GNU
Gettext doesn't compile cleanly, and dies with -Werror.
* src/Makefile.am, lib/Makefile.am, tests/atlocal.in (CFLAGS):
Include WARNING_CFLAGS here.
* lib/xstrdup.c: Include xalloc.h, so that xstrdup be declared
before being defined.

configure.in

@@ -1,5 +1,7 @@
 # Configure template for GNU Bison.                   -*-Autoconf-*-
 #
+# Copyright 2001  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 of the License, or
@@ -64,7 +66,7 @@ if test "${enableval}" = yes; then
   BISON_WARNING(-Wshadow)
   BISON_WARNING(-Wstrict-prototypes)
   BISON_WARNING(-Wwrite-strings)
-  CFLAGS="$CFLAGS $WARNING_CFLAGS"
+  BISON_WARNING(-Werror)
 fi
 
 # Checks for libraries.