AVR Support?

[PMunch]

Did a little bit of bisecting, apparently this commit broke compilation with 
AVR/ARC/exceptions: 
<https://github.com/nim-lang/Nim/commit/c65f95417a85a04707712a3b481ffa0b94c99437>
 and then that was rectified by 
<https://github.com/nim-lang/Nim/commit/6317e4004dded87d698b41274e31d318fe52e877>
 but after that it has the `strerror` bug.