Qt's QTemporaryFile isn't unicode-safe on Windows

Some KDE users reported problems when using a MS Windows account name with non-latin characters (japanese, chinese etc.)

"One big reason why it doesn't work is because Qt's QTemporaryFile isn't
unicode-safe on windows. See qtemporaryfile.cpp:352

char *filename = qstrdup(qfilename.toLocal8Bit());

This doesn't work when the locale doesn't contain the used characters.
And since we're storing all KTemporaryFile's in the user home dir this
is a very big problem..."