MenuBarStyle: Fix metrics, selected appearance

On Windows, this depends on qtbase's
Ia35a73274cc10b3b5a3f55573c92919f99555db0.

Change-Id: If513cefadc052cb1450554f2e6e8af2abac02734
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>