iOS: Fix logic for determining whether to exit the root event loop

Instead of trying to hook into various places where we might be in a
situation where the root event loop should exit, and then enabling the
runloop-observer, we always keep the observer active, and then do the
relevant checks whenever the run-loop exits.

The reason for checking if the event loop is running is that iOS will
enter and exit the root runloop as part of normal operation, eg due to
flicking a scroll view and switching the runloop mode, so we need to
ensure that we're actually supposed to exit the root event loop.

Change-Id: I9b84b47ee45e0c9e2b1d2ebb5a432ea92700b324
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
Windows: Do not use blend function for GL windows with alpha.

Task-number: QTBUG-34376

Change-Id: I81a5ee6ff14e5472eb1f3846577d86b615be34e0
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>