winebrowser: Fix unicode recognition

[Dmitry Timoshkov]

"André Hentschel" <nerv at dawncrow.de> wrote:

> This converts the DDE-Callbackfunction to Unicode.
> After days of winebrowser-hacking i turned it down to this clean code.
> It uses the function IsTextUnicode instead of guessing.(IsTextUnicode is guessing too, but in a cleaner way)

Please add a test case which uses mixed ansi/unicode DDE client/server
and only then start fixing the code.

-- 
Dmitry.