* [ASDisplayNode] Add safeAreaInsets, layoutMargins and related properties to ASDisplayNode
* Add layoutMargins bridged to the underlying view
* Add safeAreaInsets bridged to the underlying view
* Add fallback calculation of safeAreaInsets for old iOS versions
* Add automaticallyRelayoutOnSafeAreaChanges and automaticallyRelayoutOnLayoutMarginsChanges properties
* Add additionalSafeAreaInsets property to ASViewController for compatibility with old iOS versions
* Provide safeAreaInsets for layer-backed nodes.
This also fixes tests.
* Fix crash when insetsLayoutMarginsFromSafeArea is set from a background thread
* Changes requested at code review:
* Update documentation for layoutMargins and safeAreaInsets properties. Suggest that users set the automaticallyRelayout* flags to ensure that their layout is synchronized to the margin's values.
* Fix accessing ASDisplayNode internal structures without a lock.
* Add shortcut in -[ASDisplayNode _fallbackUpdateSafeAreaOnChildren] to skip a child when possible.
* Add shortcut in ASViewController to avoid fallback safe area insets recalculation in iOS 11. Fix fallback safe area insets recalculation when the additionalSafeAreaInsets are set.
* Add debug check that a view controller's node is never reused without its view controller, so the viewControllerRoot flag value is always consistent.
* Use getters instead of reading ivars directly in -layoutMarginsDidChange and -safeAreaInsetsDidChange.
* Minor change in CHANGELOG
* Minor change in ASDisplayNodeTests.mm
7f01b89ddc