iOS: Add potentially undefined version defines to qsystemdetection.h

Unless we're building on the 6.1 SDK some of the version defines will
not be defined in Availability.h, so we define them ourselves so that
Qt can still use them.

Change-Id: Ibb45e9f8f4e888fc57e35286bf15d2fee2c1a217
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
iOS: Implement socket notifiers.

Create the QCFSocketNotifier class in platform support
which contains shared socket notifier support for
the Cocoa and iOS plugins. Remove the old code from
the Cocoa plugin.

The Cocoa code had one QCocoaEventDispatcher-specific
call: maybeCancelWaitForMoreEvents. Create a forwarding
function that is passed to QCFSocketNotifier.

Change-Id: Ibf9bd4745ba4f577a55f13d0cc00f5ae04447405
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
iOS: Add QIOSIntegration::hasCapability function

Add the missing override, and report that we support
OpenGL (and multiple windows).

Change-Id: If95138cab9099b547d12d3dfed008bd63b6d2acf
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
iOS: Remove debug output noise

This debug information is not needed anymore, and only causes noise
when trying to debug other stuff.

Change-Id: I076826e251b84a3883e63aa7669f6e1bb55a0d1f
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>