Add read() function

[PaulStoffregen]

Request is here:
https://forum.pjrc.com/threads/34817-Timer1-read()

This needs to be done carefully. If anyone contributes this, please do not copy from the TimerOne fork where the author changed the license to GPL.

How this should work across AVR and 32 bit ARM versions is also a good question. Long-term, I want to allow TimerOne to work on all boards... so care is needed to not inadvertently expose hardware dependent behavior.

[antic-ml]

It has to be done so carefully that it has taken four years of thinking time so far before it is implemented? I'll add the required code myself, just forget it.