core: Plug leaks

The MetaWorkspaceLogicalMonitorData structs are leaked, and so is the
stamps hashtable in MetaDisplay.

https://bugzilla.gnome.org/show_bug.cgi?id=789984

src/core/display.c

@@ -1138,6 +1138,7 @@ meta_display_close (MetaDisplay *display,
    */
   g_hash_table_destroy (display->xids);
   g_hash_table_destroy (display->wayland_windows);
+  g_hash_table_destroy (display->stamps);
 
   if (display->leader_window != None)
     XDestroyWindow (display->xdisplay, display->leader_window);

src/core/workspace.c

@@ -99,6 +99,7 @@ workspace_logical_monitor_data_free (MetaWorkspaceLogicalMonitorData *data)
 {
   g_clear_pointer (&data->logical_monitor_region,
                    meta_rectangle_free_list_and_elements);
+  g_free (data);
 }
 
 static MetaWorkspaceLogicalMonitorData *