Optimization ideas

[superctr]

• Currently I measured the runtime to 10 lines if 4 FM channels are active but not updated
• [x] Trigger priority calculation based on channel allocation/deallocation rather than always doing it on each frame.
• [ ] Skip pitch calculation routine when not needed. I think checking a bitmask of the following new flags:
  • pitch envelope active. Set by new note, cleared if pitch envelope is finished or not active.
  • portamento active. Set by new note, cleared if portamento is completed
  • pitch update triggered by new note, dtn or trs commands