New windowing code

[Takuma Murakami]

> > - To get things to compile, I had to make the attached smallchange.txt
> 
> I think that change is not necessary.  I changed the type of
> HandleCustomWM_COMMAND from int to Bool in my previous
> commit on few days ago.  Is the definition of the function in
> winprefs.c typed as Bool?

I confirmed the problem after 'make clean', with
Harold's correction.

Takuma Murakami