Windows logging: Fix check for console applications.

The old code used to check for usingWinMain, which is not set when
Qt is used within a DLL. Try to check for presence of stderr
by checking for a console window or a redirected stderr-handle.

Task-number: QTBUG-32044
Change-Id: I87893c3438f5e92d73488e9c25b95cbfeaacc1f6
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>