AVR Support?

[PMunch]

Hmm, after reading about `quirky` and `goto` exceptions I'm not quite sure if I 
understand the difference. They even reference the same source paper in their 
descriptions, and it seems like `goto` is just the more mature version. I've 
been using `os:any` with great success on the Teensy (atmega32u4), although 
I've been staying away from exceptions for size constraint reasons. I think it 
might be time to write some better guides/documentation for using Nim on AVR, 
hmm..