Debug Channels trashed

[Mike Hearn]

> Good question. I don't know.
> 
> Possibly the window procedure is declared using a calling convention that
> somehow mangles even the wrapper stack, so we're popping garbage off it
> into %ebx. But I'm out of ideas for now.

What I would suggest is putting some stack padding between the saved 
registers and the window proc parameters. If that makes a difference 
submit it to wine-patches, as it's likely that the padding has been 
blasted rather than the register save area.