IEEE1588 improvements for PTP

[HedgeHawk]

Hey, thank you for this awesome library! I just saw PR https://github.com/ssilverman/QNEthernet/pull/57 and read that there is some ongoing work on a new branch for IEEE1588. Last year, I implemented some new functionality that we needed for our PTP library and fixed some bugs in the timer code during verification. We also built some examples along the way for Pulse Per Second (PPS) in and out and timer adjustments that may come in handy. I currently don't have the time to rebase this on the master branch, but I hope some snippets of the code help to improve the ongoing work.

[ssilverman]

Thanks for this. I have a local copy that I try to keep up-to-date with master. I’ll see where your changes fit in.