iOS: clear focus object when resigning first responder status

Instead of deactivating the window when we resign first
responder status, we now leave it focused, and
tell it to clear its focus object instead.
This will work better with the rest of Qt, which expects
a window to have focus when its in front.

Change-Id: I6fcc232467af306b791a834f4843bfd2786b206f
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
iOS: bugfix touch events when not using alien

It seems that 130ee40b broke touch handling for
non-alien QWindows. For those cases, a QWindow that is a
child of another QWindow will get its own UIView to
back it up. The current code did not take this into
account when calculating the global coordinates of
touch events. Instead we need to search for the
top level QWindow it might be inside before we find the
view that acts as the "desktop" for it.

Change-Id: Ie3c19bf86c92fa3f247a0764116830e91b8322d2
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>