Fix bug #9302365 HorizontalScrollView is not RTL aware

- make FrameLayout capable of forcing a Gravity.LEFT (when there will be
only one child with Gravity.RIGHT and wider than its parent like for
HorizontalScrollView)
- fix onLayout() so that it is forcing Gravity.LEFT if needed and
setting correctly the initial mScrollX
- also add restore/save from an instance state (by saving if the layout
is RTL and the scroll position)

Change-Id: Ida7ff4654c6a54a1696c2575af46f044dd1aabc8