MightyCore v2.2.1

Changelog:

• Fix issue where Wire timeout were always enabled
  • Should be default off
• Updates to MCUdude corefiles (Updates currently present in ArduinoCore-avr or certain PRs waiting to be merged)
  • Use ADC instead of combining ADCL and ADCH
  • Improve wiring_shift function
  • Remove unnecessary if branch (because length is checked in while statement below the if-clause)
  • Add bitToggle macro
  • Add parenthesis around 'bitvalue' allowing correct macro expansion
  • Add null pointer check to String destructor
  • Improvements to HardwareSerial.cpp
  • Improve how TXCn bit is cleared in USCRnA register
  • Update abi and new
  • ISO c++ doesn't support binary contants