3.18 kernel for Android

[Jason A. Donenfeld]

Hi folks,

I've backported WireGuard using our series of disgusting, horrifying,
and repulsive [1] compat.h hacks to kernel 3.18. WireGuard now
supports all kernels ≥3.18. This should allow for building the module
for many Android phones.

If nothing terrible happens, this will be released as part of the next snapshot.

Jason

[1] https://git.zx2c4.com/WireGuard/tree/src/compat.h