crash_reporter: Add Android.mk

This builds:
* crash_reporter: Client for collecting crash data.
* crash_sender: Installs the script for sending crash reports to the server.
* warn_collector: Flex client for monitoring /var/log/messages for kernel
  warnings.
* init.crash_reporter.rc: Init script for setting up crash reporting.
* crash_reporter_logs.conf: Conf file for handling core dumps.
* Unit tests for the different crash collectors.  These currently build, but
  not all of them pass as the crash reporter client isn't properly configured
  yet.

Bug: 22486906
Change-Id: I9337a566f35955d1d41ae94d535eb9e9730bbeb1