libbinder: Support sp<Flattenable> in SafeInterface

Adds support for sending and receiving sp<Flattenable> parameters (such
as sp<Fence> and sp<GraphicBuffer>) as part of a SafeInterface.

Test: New test in binderSafeInterfaceTest
Change-Id: I36ba19c7f121771e9a7acfde9ed164e1cd3200b3
2 files changed