WindowServer: Let menu objects reference the WSClientConnection by pointer.

Since these are owner/ownee relationships, there's no need for indirection.

WindowServer/WSMenuBar.cpp

@@ -2,8 +2,8 @@
 #include "WSMenu.h"
 #include "WSMenuItem.h"
 
-WSMenuBar::WSMenuBar(int client_id, int menubar_id)
-    : m_client_id(client_id)
+WSMenuBar::WSMenuBar(WSClientConnection& client, int menubar_id)
+    : m_client(client)
     , m_menubar_id(menubar_id)
 {
 }