Add compatibility with 8devices NUY

Hi,

This is part of integration of NUY hardware support to Arduino Yun repositories.
This PR adds:

 * NUY platform support
 * Build target 'Yun_compat' for building Yun and NUY images with compatible kernel modules
 * Add BOSSA to default config
 * Patch to busybox init, that allows use of /dev/ttyATH0 for programming Arduino with serial bootloader