Fix QScreen::grabWindow for multiple screens on Mac

QScreen::grabWindow() would only with the primary screen on Mac, if you
tried to grab a secondary one then it would end up with a blank pixmap.

Change-Id: I24f604051835db96286c693f5ed60a2633b6528e
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Fallback to the original application font handling

When Qt is built for 10.8 but then used on a machine before 10.8 then
it was not falling back correctly when an application font was added.

Change-Id: I0f05226cdbcfa36621bb1b3aa2f2cd60e714dfdf
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Improve QLoggingCategory documentation

Change-Id: I142e954cc3622643d80b8efd3b1d659c11d4e239
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Remove default label for QtMsgType

Adding another category will most likely require a dedicated
handling anyway, so better let the compiler warn about it.

Change-Id: I323ca1250d82e33c086f1930e1df0a6337d6f16f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>