newer impl of degamma()

I was recently exploring the code and noticed the degamma() method has been replaced in the C lib with the following data table implementation:
https://github.com/todbot/blink1-tool/blob/775261ade8b525ca6f7f86a61bac8082476b44ea/blink1-lib.c#L676

I'll be glad to do a simple port if you're interested .