update to modern gdc compatibility

datatypes/datatypes.d

@@ -34,7 +34,7 @@ int main()
     writefln("char (%d)\twchar (%d)\tdchar (%d)",
             char.sizeof, wchar.sizeof, dchar.sizeof);
 
-    writefln();
+    writefln("");
     writefln("char min: %d\tmax: %d", char.min, char.max);
     writefln("wchar min: %d\tmax: %d", wchar.min, wchar.max);