wireguard: bump to 20180118

Bump to latest wireguard release snapshot:

9a93a3d version: bump snapshot
7bc0579 contrib: keygen-html: update curve25519 implementation
ffc13a3 tools: import new curve25519 implementations
0ae7356 curve25519: wire up new impls and remove donna
f90e36b curve25519: resolve symbol clash between fe types
505bc05 curve25519: import 64-bit hacl-star implementation
8c02050 curve25519: import 32-bit fiat-crypto implementation
96157fd curve25519: modularize implementation
4830fc7 poly1305: remove indirect calls
bfd1a5e tools: plug memleak in config error path
09bf49b external-tests: add python implementation
b4d5801 wg-quick: ifnames have max len of 15
6fcd86c socket: check for null socket before fishing out sport
ddb8270 global: year bump
399d766 receive: treat packet checking as irrelevant for timers

No patch refresh required.

Compile-tested-for: ar71xx
Run-tested-on: ar71xx Archer C7 v2

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>