skins(Win): a proper way to terminate vlc

This fixes vlc hanging when closed via the popupmenu in the taskbar.

modules/gui/skins2/win32/win32_factory.cpp

@@ -69,7 +69,7 @@ LRESULT CALLBACK Win32Proc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam )
             if( wParam == SC_CLOSE )
             {
                 Win32Loop *pLoop = (Win32Loop*)Win32Loop::instance( p_intf );
-                pLoop->exit();
+                libvlc_Quit( p_intf->p_libvlc );
                 return 0;
             }
             else