With added support for ATmega16U4/32U4 (Leonardo)
- Original Thread: https://forum.arduino.cc/index.php?topic=117425.0
- Original Copyright:Copyright (c) 2012 Sam Knight
- Modified for support for ATmega16U4/32U4 (Leonardo) by "Pierre" Oct 23, 2013. Forked from https://code.google.com/archive/p/arduino-pwm-frequency-library/issues/2
- Modified to avoid changing prescaler when changing frequency by Paul Abbott - 2017