Mir 0.6.0

- mirclient ABI unchanged at 8. Clients do not need rebuilding.
- mirserver ABI bumped to 24. Servers need rebuilding, but probably don't
  need modification:
  . Host lifecycle event listener for nested servers introduced.
  . Add query function to BasicSurface.
  . The (deprecated) function the_ipc_factory() is now removed.
  . Removed legacy support for overriding the focus controller or the
    frontend shell.
  . Added support for a common type for managing fd's.
  . Moved testdraw library to examples directory.
  . Added support for droping stale frames when a surface becomes exposed.
- Enhancements:
  . Split underlying data transport out of MirSocketRpcChannel.
  . Introduced two new client-side functions : mir_surface_get_focus and
    mir_surface_get_visibility.
  . Added symbolic names for cursors.
  . Made "shared" code a true shared library.
  . Provide linker scripts to control symbols exported by [mesa|android]
    libmirclientplatform.
  . Correct xcursor loader test to fail properly instead of segfaulting.
  . Make mir::Fd type copy constructible.
  . Miscellaneous packaging related enhancements.
  . Miscellaneous build related enhancements.
  . Added automated test cases for detecting ABI breakage.
  . examples/fingerpaint: Enable frame dropping so it's faster and more
    responsive.
  . mirprotobuf folded into new libmircommon.
  . Don't propagate exceptions to graphics driver code.
  . Dropped unused/minimally used dependencies : boost-filesystem,
    boost-thread, boost-chrono, boost-regex.
  . platform: provide support for customizing Mir's behavior when a
    fatal_error occurs.
  . Expose an interface for touch visualization.
- Lots of bug fixes (see below)