Avoid "Bogus FL_MOVE/FL_DRAG events" (#76)

Fix sending bogus events if CONSOLIDATE_MOTION is on.

Backported from 1.4 (master):
  commit 7a7f3c3324.

src/Fl_x.cxx

@@ -210,7 +210,7 @@ static void do_queued_events() {
   // we send FL_LEAVE only if the mouse did not enter some other window:
   if (!in_a_window) Fl::handle(FL_LEAVE, 0);
 #if CONSOLIDATE_MOTION
-  else if (send_motion == fl_xmousewin) {
+  else if (send_motion && send_motion == fl_xmousewin) {
     send_motion = 0;
     Fl::handle(FL_MOVE, fl_xmousewin);
   }