Enabling top layout guide adjustment

The topLayoutGuideAdjustmentEnabled behavior flag affects topLayoutGuideViewController. Setting topLayoutGuideAdjustmentEnabled to YES enables the new behavior.

topLayoutGuideAdjustmentEnabled is disabled by default, but will eventually be enabled by default and the flag will eventually be removed.

Swift

flexibleHeaderViewController.topLayoutGuideAdjustmentEnabled = true

Objective-C

flexibleHeaderViewController.topLayoutGuideAdjustmentEnabled = YES;