Mir 0.14.0

- ABI summary: All clients and all servers need building;
  . Mirclient ABI bumped to 9
  . Mirserver ABI bumped to 32
  . Mircommon ABI bumped to 5
  . Mirplatform ABI bumped to 8
- Enhancements:
  . mir_demo_server: tweaks, features and improvements
  . More MirEvent-2.0 related changes and unifications
  . New SurfaceInputDispatcher to replace the android InputDispatcher
  . New Threaded dispatcher for Dispatchable added
  . Rework of the relationship of surfaces and buffer streams to allow
    attaching multiple buffer streams to a surface.
  . Preparation work for new buffer semantics
  . fd leaks in tests eliminated and leak check activated for unit and
    integration tests
  . Further TSAN reported issues removed
  . Preparation work for mir-on-x: splitting of mesa platform in common
    and KMS parts
  . Further rework of input stack focused on test infrastructure
  . Persistent id request for surfaces added
  . Integration-tests cleaning: switch tests to in-process server
  . A first end-to-end input test added in privileged-tests
  . "mesa" platform renamed to "mesa-kms" (LP: #1381330)
  . [enhancement] Mir servers should allow client connections only after
    server start-up has finished (LP: #1451844)
  . build-dependency on g++-4.9 dropped (LP: #1452320)
- Bug fixes: See below.