Prior Incrementing/decrementing by fixed steps (typically 10) means large
perceptual jumps at low brightness and small jumps at high brightness. This
change moves to a geometric progression, closer at the bottom of the range and
widely spaced at the top.
While it could be done as a relative jump (incrementing by bri/4 and
decrementing bri/5 works quite well), it makes for irregular behavior when
moving back and forth.
...in cfg.cpp the if statement used "IRPIN" (which is consistent to all other PIN names), but on the declaration-side "IR_PIN" was used.
Changed all occurences of "IR_PIN" to "IRPIN".