Don't replay presses which are required f/ motions

When trying to doAction(ButtonPress, ...), we check whether the
action would hit for type==MotionNotify.
In this case we do nothing but return "true" to tell the caller that
this event is "for us". Otherwise the event would be replayed to the
client and there'd go out MotionNotify grabs.

tl;du: This fixes MoveX actions.

src/Keys.cc

@@ -555,6 +555,10 @@ bool Keys::doAction(int type, unsigned int mods, unsigned int key,
     if (!temp_key && isdouble)
         temp_key = next_key->find(type, mods, key, context, false);
 
+    if (!temp_key && type == ButtonPress && // unassigned button press
+        next_key->find(MotionNotify, mods, key, context, false))
+        return true; // if there's a motion action, prevent replay to the client (but do nothing)
+
     if (temp_key && !temp_key->keylist.empty()) { // emacs-style
         if (!saved_keymode)
             saved_keymode = m_keylist;