Mir 0.11.0

- Packaging changes:
  . Due to changes in the Mir driver model the client platforms are no
    longer versioned by soname. Thusly libmirplatform5driver-(mesa|android) is
    replaced by mir-client-platform-(mesa-android). A new package
    mir-client-platform-mesa-dev is introduced containing headers
    previously in mirplatform-dev.
- Enhancements:
  . Lots more major plumbing in the Android code, on the path to
    supporting external displays.
  . Add support for clang 3.6.
  . Major redesign of server classes in mir::shell,scene and friends
    (still in progress).
  . Added client API for creating dialogs and tooltips.
  . Added new surface states: mir_surface_state_hidden and
    mir_surface_state_horizmaximized.
  . Performance: Use optimally efficient fragment shading when possible.
  . Performance: (Desktop) Composite using double buffering instead of
    triple to reduce visible lag.
  . mir_proving_server: Can now resize windows from any edge or corner
    using the existing Alt+middlebuttondrag.
  . mir_proving_server: Added some demo custom shaders (negative and
    high contrast modes: Super+N/C).
  . mir_proving_server: Can now close clients politely via Alt+F4.
  . Added MirPointerInputEvent (part of the new input API, the old
    MirMotionEvent is still supported also for now).
- ABI summary: Servers need rebuilding, but clients do not;
  . Mirclient ABI unchanged at 8
  . Mircommon ABI unchanged at 3
  . Mirplatform ABI bumped to 6
  . Mirserver ABI bumped to 29
- Bug fixes: See below.