* A demo application has been added, it allows to directly test the
without the need of an external tool.
* Loading games:
- Add the set_medias(), load_medias() and set_current_media() methods
to Core and load the given medias (if any) in Core.init().
- Remove load_game() and prepare() Core methods from the public API as
they are now used indirectly.
- This should simplify loading games for the users of the library.
* Logging:
- Add the Core.log() signal which will emit a GLib compatible logging
message with the Libretro core's name as the log domain.
- Add retro_g_log() to simply handle Core.log() by outputing the logs
in the expected unstructured GLib fashion.
- Remove LogLevel, Log and FileStreamLog as they are now useless.
* Add CoreView as a prototype of a single widget to handle most inputs
and outputs of a core and use it in the demo.
* Add CoreDescriptor.get_uri().
* Make CairoDisplay.set_core() and Make PaPlayer.set_core() accept null.
* Fix the transmission of keyboard events to the Libretro core.
* Rotation and many methods of Core are ported to C.
* Bugs fixed:
777489 Refactor the whole API
780919 Add a demo application
782501 retro-gtk: Port to C
782504 retro-gtk: Improve Libretro core logging
782505 retro-gtk: (on_input_state): should not be reached
782772 retro: Libretro cores should have an appropriate save directory
