can be done in other ways instead of being held back by this old input
recording format - was decided along with Themaister that we want to
arrive at a codebase more easily maintained by all
- move shader flags from the video drivers to the context drivers
- rework config_load_shader_preset() from configuration.c into retroarch_load_shader_preset() in retroarch.c with proper compatibility check
- implicitly call retroarch_load_shader_preset() in retroarch_get_shader_preset() once per core/content life cycle
- use video_shader_is_supported() instead of video_driver_test_all_flags() where appropriate
- remove GFX_CTX_FLAGS_NONE because it is meaningless
- video_shader_parse_type()'s fallback only worked for NULL paths and was wrongly used, now returns RARCH_SHADER_NONE like video_shader_get_type_from_ext().
- video_shader_get_type_from_ext() should not be checking video driver flags, this is instead done by video_shader_is_supported()
- video_driver_get_all_flags() did not actually 'get' flags, changed to video_driver_test_all_flags()
workaround for crash due to glcore not always using at least OpenGL 3.2
- only use filestream_exists immediately before filestream_delete or
any other genuine filestream-related operations - when just checking
if a path exists on the filesystem, just use path_is_valid - faster
- allow savestates on hardcore
- fix weird conditions happening due to having two implementations
- fix popup saying state was loaded when starting a game with achievements hardcore after a game with no achievements
- fix rewind not working when loading games with no achievements after loading games with achievements hardcore
- use STRLEN_CONST for constant strings, translates to sizeof
which should be computed at compile-time
- found some places where we are needlessly calling strlen two
times instead of just once
