CloseGuard: finalizers for closeable objects should log complaints

Introducing CloseGuard which warns when resources are implictly
cleaned up by finalizers when an explicit termination method, to use
the Effective Java "Issue 7: Avoid finalizers" terminology, should
have been used by the caller.

libcore classes that can use CloseGuard now do so.

Bug: 3041575
Change-Id: I4a4e3554addaf3075c823feb0a0ff0ad1c1f6196
21 files changed