Patch to compile on C89 compilers.

src/video/x11/SDL_x11window.c

@@ -944,9 +944,10 @@ SetWindowActive(_THIS, SDL_Window * window)
     Atom _NET_ACTIVE_WINDOW = data->videodata->_NET_ACTIVE_WINDOW;
 
     if (X11_IsWindowMapped(_this, window)) {
+        XEvent e;
+
         SDL_assert(data->user_time != 0);  /* should be set by _some_ event by now. */
         /*printf("SDL Window %p: sending _NET_ACTIVE_WINDOW with timestamp %lu\n", window, data->user_time);*/
-        XEvent e;
 
         SDL_zero(e);
         e.xany.type = ClientMessage;