compat: missing #include, fix warning

compat/strverscmp.c

 /* Compare strings while treating digits characters numerically.
    Copyright (C) 1997, 2002, 2009 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
-   Contributed by Jean-Franois Bignolles <bignolle@ecoledoc.ibp.fr>, 1997.
+   Contributed by Jean-François Bignolles <bignolle@ecoledoc.ibp.fr>, 1997.
 
    The GNU C Library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
@@ -18,6 +18,10 @@
    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
    02111-1307 USA.  */
 
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
 #include <stdint.h>
 #include <string.h>
 #include <ctype.h>