Cocoa QPA Menu: Clear menu items' Cocoa ancestor on destruction

Valid for both the item and the menu destructions.

Task-number: QTBUG-38685
Change-Id: I024b93c8bb8facefeaad5e8b6c7be6bf049898ea
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Fix more double release in QTimeZone on Mac

Several objects are released without being retained.
This causes double free crash.

Task-number: QTBUG-37582
Task-number: QTBUG-35890
Change-Id: Ic64419c22ab555ba77ada1864feaff247798d3ad
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Revision new signal

As it's meant for QML anyways, this allows it to coexist peacefully with
existing code.

Task-number:  QTBUG-29806
Change-Id: Ib04993f47eb2f9f7fc49c4a5400f18f9682a7aaa
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Update changelog for iOS

Change-Id: Id0bbfa4aa1420cddbcc9950757c1c5fc83d744c1
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Add a comment about not obvious code in VariantData.

Change-Id: I943af28c47b396aa35173da2a1294b86c8a522fa
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>