riched20: register ListBox & ComboBox classes

[Cihan Altinay]

Hi,
> This patch partially implements the undocumented REExtendedRegisterClass()
> function by registering the two missing classes. That way MS Office 2003 and
> probably other programs that rely on these classes display dialogs
> completely which were empty before.
>
> Changelog:
>     Cihan Altinay 
>     Partially implement REExtendedRegisterClass() to register missing window
>     classes so that applications relying on them don't get confused.

It seems this patch was ignored and I would appreciate some comments because
I haven't done much wine development yet (and probably made a lot of mistakes).
Basically, I did some reverse engineering to see what is going on under Windows
and implemented the (de)registration of the two classes accordingly. The effect
of the patch can be seen in the attached screenshots which is the Options
dialog of MS PowerPoint 2003.
I agree that a patch that makes the controls actually work would be better :-)

Cheers,
Cihan