[amiwm] Implement a keyboard shortcut to move a client to a different screen

This allows a keyboard shortcut to move a client to a different amiwm
screen.  That way when you have things like Firefox restart every window
in a single screen, you can quickly move screens to where they should be.

icon.c

@@ -156,12 +156,16 @@ void reparenticon(Icon *i, Scrn *s, int x, int y)
   i->next=s->icons;
   s->icons=i;
   if(i->client) {
+#if 1
+    reparent_client(s, i->client);
+#else
     i->client->scr=s;
     if(i->client->parent != i->client->scr->root)
       XReparentWindow(dpy, i->client->parent, s->back,
 		      i->client->x, i->client->y);
     setstringprop(i->client->window, amiwm_screen, s->deftitle);
     sendconfig(i->client);
+#endif
   }
   if(os)
     selecticon(i);