Add prototype for CheckDefaultMap().

Those warnings disappear accordingly:
|   CC     parseutils.lo
| parseutils.c:742: warning: no previous prototype for ‘CheckDefaultMap’
|   CC     xkbscan.lo
| xkbscan.l: In function ‘XKBParseString’:
| xkbscan.l:220: warning: implicit declaration of function ‘CheckDefaultMap’
| xkbscan.l:220: warning: nested extern declaration of ‘CheckDefaultMap’

Reviewed-by: Dirk Wallenstein <halsmit@t-online.de>
Signed-off-by: Cyril Brulebois <kibi@debian.org>
diff --git a/src/xkbcomp/parseutils.h b/src/xkbcomp/parseutils.h
index 9cf5097..c0a78df 100644
--- a/src/xkbcomp/parseutils.h
+++ b/src/xkbcomp/parseutils.h
@@ -179,6 +179,8 @@
 
 extern int XKBParseString(const char *string, XkbFile ** pRtrn);
 
+extern void CheckDefaultMap(XkbFile * maps);
+
 extern XkbFile *CreateXKBFile(int /* type */ ,
                               char * /* name */ ,
                               ParseCommon * /* defs */ ,