don't accept variablenames with index > max_loop

making them default to game_config::max_loop isn't useful im most cases.

src/variable_info.cpp

@@ -164,7 +164,7 @@ namespace
 		}
 		if(res > int(game_config::max_loop))
 		{
-			res = game_config::max_loop;
+			throw invalid_variablename_exception();
 		}
 		return res;
 	}