patch for #4796

Hello,

this is a cleaned up patch for bug #4796. It fixes dialog titles for
documents containing non-ascii characters.

I also changed the XAP_Dialog_Modeless::BuildWindowName signature
because the return value was never used and having pWindowName as
parameter AND return value is a little ambiguous IMHO.

It would be really cool if you could look at it because it's been in CVS
for quite some time (2003-05-09).

Thanks,
Rob