Replace ShellXFixesCursor with MetaCursorTracker

Mutter now includes an object with the same purpose and functionality
as ShellXFixesCursor, so we can replace our XFixes code with it
and work under wayland too.

https://bugzilla.gnome.org/show_bug.cgi?id=705911

src/shell-util.c

@@ -431,3 +431,13 @@ shell_util_wake_up_screen (void)
   first_keycode = !first_keycode;
   gdk_error_trap_pop_ignored ();
 }
+
+void
+shell_util_cursor_tracker_to_clutter (MetaCursorTracker *tracker,
+                                      ClutterTexture    *texture)
+{
+  CoglTexture *sprite;
+
+  sprite = meta_cursor_tracker_get_sprite (tracker);
+  clutter_texture_set_cogl_texture (texture, sprite);
+}