Fix size restore on unfullscreening

When a window is restored back to normal resize from fullscreen mode, its
geometry got smaller by its titlebar's size. Fix this by adding the titlebar
geometry to the client's geometry at the correct place.

Thanks to anrxc for reporting this and helping me debug it.

Signed-off-by: Uli Schlachter <psychon@znc.in>

client.c

@@ -1038,7 +1038,7 @@ client_set_fullscreen(lua_State *L, int cidx, bool s)
         {
             /* The titlebar was banned, unban! */
             titlebar_unban(c->titlebar);
-            geometry = c->geometries.fullscreen;
+            geometry = titlebar_geometry_add(c->titlebar, 0, c->geometries.fullscreen);
             c->fullscreen = false;
             client_set_border_width(L, cidx, c->border_width_fs);
         }