SEQ64 V2.3.1

Fixed a very old issue where, because program changes are internally treated as a type of CC, they could be merged when forming hooks or loops, even if their values were different (default accepted delta of 1). This is desired behavior for CCs like volume and pan, but obviously not for program changes where instrument 3 isn't "close to" instrument 4. I'm not sure how nobody ran into this bug before in the ~8 years since it's been around, but it's fixed now!