Wireguard backport to 2.6.3x kernels

[Jason A. Donenfeld]

Hi Igor,

It's certainly possible to backport. At the moment I'm focused on
moving the project forward with other tasks, so it's not a good use of
my time, but if you'd like to give this a stab, I'd happily take
non-invasive patches that only touch the compat/ directory. Just keep
in mind that you'll need to support all kernels in between your target
and the current minimum.

Regards,
Jason