skins2(Win32): add a way to hide the popup menu on systray

Rightclicking on the vlc icon in systray displayed the popup menu,
but till now, there was no means to hide it without first executing
something from this menu

This patch uses leftclick as a way to hide this popupmenu

modules/gui/skins2/win32/win32_factory.cpp

@@ -86,6 +86,8 @@ LRESULT CALLBACK Win32Proc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam )
             if( (UINT)lParam == WM_LBUTTONDOWN )
             {
                 p_intf->p_sys->p_theme->getWindowManager().raiseAll();
+                CmdDlgHidePopupMenu aCmdPopup( p_intf );
+                aCmdPopup.execute();
             }
             else if( (UINT)lParam == WM_RBUTTONDOWN )
             {