CActiveScheduler::Replace in UI thread

This took me a while to realize, so I though I'd share it:

If you want to install a custom active scheduler in a UI
thread, you have to derive your scheduler from CCoeScheduler
(and not, e.g., CBaActiveScheduler), otherwise you'll
get no UI events. And if you override the WaitForAnyRequest
function, call CCoeScheduler::WaitForAnyRequest in it.

I assume that the CCoeScheduler is doing the requesting
of UI events.