menu: Fix for menu tracking problem version 2

[Andrew de Quincey]

> This patch attempts to replicate this functionality. It resets the captured
> window immediately after issuing the WM_DRAWITEM message, in case the
> application has changed it. Note this code only occurs on WM_OWNERDRAW menu
> items, as this should be the only situation where this problem can occur.

Hold on; I didn't notice before, but this causes other mouse-related problems. 
Sigh. New patch later.