mod_lua: If a regex fails, return false plus an error message as second return value. Also fix some functions who weren't always returning a value.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1422373 13f79535-47bb-0310-9956-ffa450edef68

modules/lua/mod_lua.c

@@ -116,6 +116,7 @@ static const char *scope_to_string(unsigned int scope)
 #endif
     default:
         ap_assert(0);
+        return 0;
     }
 }