binder: add support for Ion

Add classes to allocate from the Ion memory manager.

Change-Id: I72ad0c95a06c47a5d7441f7f699ba1462e1b8632

binder: Get rid of old flag

MAP_LOCKED_MAP_POPULATE is an outdated flag that is not used
anymore. Get rid of this flag in MemoryHeapIon

Change-Id: Ib43d2a413f5177b98a66bf3ef1476db8caef56cd