[SDL] unicode conversion not working on KEYUP on win NT

[Sam Lantinga]

> That's fair enough if that is the intention. But I guess it should then
> consistently have unicode set to 0. Actually, the fact that unicodes
> are delivered with KEYDOWN is confusing, as they don't correspond to
> the up/down pattern as you describe (a seperate type of message would
> have been better).

Fair enough.  I'll fix the keyboard drivers to only do key translation
on key-down, which will speed up keyboard processing a little bit.

Thanks!
	-Sam Lantinga, Lead Programmer, Loki Entertainment Software