wireguard: bump to 0.0.20180620

wireguard: bump to 0.0.20180620

0bc4230 version: bump snapshot
ed04799 poly1305: add missing string.h header
cbd4e34 compat: use stabler lkml links
caa718c ratelimiter: do not allow concurrent init and uninit
894ddae ratelimiter: mitigate reference underflow
0a8a62c receive: drop handshake packets if rng is not initialized
cad9e52 noise: wait for crng before taking locks
83c0690 netlink: maintain static_identity lock over entire private key update
0913f1c noise: take locks for ss precomputation
073f31a qemu: bump default kernel
bec4c48 wg-quick: android: don't forget to free compiled regexes
7ce2ef3 wg-quick: android: disable roaming to v6 networks when v4 is specified
9132be4 dns-hatchet: apply resolv.conf's selinux context to new resolv.conf
41a5747 simd: no need to restore fpu state when no preemption
6d7f0b0 simd: encapsulate fpu amortization into nice functions
f8b57d5 queueing: re-enable preemption periodically to lower latency
b7b193f queueing: remove useless spinlocks on sc
5bb62fe tools: getentropy requires 10.12
4e9f120 chacha20poly1305: use slow crypto on -rt kernels on arm too

Compiled-for: ar71xx, lantiq
Run-tested-on: ar71xx Archer C7 v2 & lantiq HH5a

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