ART: Track Flush & Close in FdFile

Implement a check that aborts when a file hasn't been explicitly
flushed and closed when it is destructed.

Add WARN_UNUSED to FdFile methods.

Update dex2oat, patchoat, scoped_flock and some gtests to pass with
this.

(cherry picked from commit 9433ec60b325b708b9fa87e699ab4a6565741494)

Change-Id: I9ab03b1653e69f44cc98946dc89d764c3e045dd4
19 files changed