DilloURL has a dtor.

It is the same as the original free function.  But this
will let me put some ownership on various members and slowly
start to C++ify this core type.

src/history.cc

@@ -154,7 +154,7 @@ void a_History_freeall(void)
    int i;
 
    for (i = 0; i < history_size; ++i) {
-      a_Url_free(history[i].url);
+      delete history[i].url;
       dFree(history[i].title);
    }
    dFree(history);