vo: signal VOCTRL_REDRAW in a less sensitive spot

Windows works totally differently than the other backends and is
sensitive to synchronization issues since it runs its control on a
separate thread. The spot where this was originally placed was a perfect
storm of causing resize weirdness because it was before the flip and
right after the redraw. Ideally, this is known to the windowing backend
before the flip actually happens so just move this out to before the
do_redraw call. It makes no practical difference for the one user of
this and sidesteps the implementation differences that exist on Windows.
Fixes fc9d1ca.

video/out/vo.c

@@ -1098,7 +1098,6 @@ static void do_redraw(struct vo *vo)
     mp_mutex_unlock(&in->lock);
 
     vo->driver->draw_frame(vo, frame);
-    vo->driver->control(vo, VOCTRL_REDRAW, NULL);
     vo->driver->flip_page(vo);
 
     if (frame != &dummy && !vo->driver->frame_owner)
@@ -1180,6 +1179,7 @@ static MP_THREAD_VOID vo_thread(void *ptr)
         if (send_pause)
             vo->driver->control(vo, vo_paused ? VOCTRL_PAUSE : VOCTRL_RESUME, NULL);
         if (wait_until > now && redraw) {
+            vo->driver->control(vo, VOCTRL_REDRAW, NULL);
             do_redraw(vo); // now is a good time
             continue;
         }