Eliminate CrashData and friends.

(CrashData was a custom-marshalled crash-info class used for a server crash
reporting system I am deprecating).  Use ApplicationErrorReport.CrashInfo
instead to report crash details (mostly the stack trace) from RuntimeInfo to
ActivityManagerService, since we're likely to need the crash information in
that form anyway.

Remove the (long-disabled) flags and support for the "Debug" button
in the crash dialog.

Further gut the ICheckinService interface by removing the crash-reporting
APIs (and everything that calls them), plus the synchronous checkin()
method (which has been stubbed out for a while now).

A new dropbox-based crash reporting system is in the works, but not part
of this change.