Support for main game loop inversion of control

Closes #26

See merge request !38

debug assertions for copy_fast

Support for SIMD operations for RGG1555

Closes #45

See merge request !45

Support for PyPi

Closes #43

See merge request !44

Without flush we would might be loosing some bytes in writing.
This is explicitly stated in https://doc.rust-lang.org/std/fs/struct.File.html.

Also adds more explicit error handling in state related code.

Also adds flush operation after writing to file.

Allows speedup and FPS measuring.

Uses a different file for the C structs of Libretro.
Makes it easier to manage the structure these structures.

Fix Libbretro issue in loading of base emulator info

See merge request !43