Ability to offer other TIMERS for milllis() and micros() like TIMERA0 or RTC

[LaurentR59]

Hi

Due to TIMERA0 and RTC availability on AV0 parts it should be a very good improvement step to offer a way to use TIMERA0 for exemple as millis() /micros() source like we can find in DXCORE library. ( should be manage by change request files like timer.h + wirings files )

On small parts like X08 ones it let 3 precious TIMER B fully available keeping millis() & micros() mapped on another timer (like A0)

On AVR DX parts it works like a charme and let free of use 3 TIMERS B so why n,ot on MEGACOREX as improvement?

Regards
Laurent