Use enumerated types whenever possible

[HertzDevil]

• [ ] apu_machine_t
• [ ] arp_scheme_mode_t
• [ ] buffer_event_t
• [ ] chan_id_t
• [ ] chip_level_t
• [ ] chunk_type_t
• [ ] color_items_t
• [x] column_t
• [ ] command_t
• [x] cursor_column_t
• [ ] EDIT_STYLES
• [ ] edit_t
• [x] effect_t
• [ ] frame_edit_pos_t
• [ ] inst_type_t
• [x] machine_t
• [ ] note_prio_t
• [ ] note_t
• [x] paste_mode_t
• [x] paste_pos_t
• [ ] PATHS
• [ ] play_mode_t
• [ ] render_end_t
• [ ] s5b_mode_t
• [ ] scroll_t
• [x] sel_condition_t
• [ ] seq_setting_t
• [ ] seq_state_t
• [ ] sequence_t
• [ ] transpose_t
• [x] vibrato_t
• [ ] vrc7_command_t

[HertzDevil]

hold off until 0.5.0 which presumably uses a newer compiler and supports enum classes