wireguard: bump to 0.0.20180513

wireguard: bump to 0.0.20180513

6b4a340 version: bump snapshot
faa2103 compat: don't clear header bits on RHEL
4014532 compat: handle RHEL 7.5's recent backports
66589bc queueing: preserve pfmemalloc header bit
37f114a chacha20poly1305: make gcc 8.1 happy
926caae socket: use skb_put_data
724d979 wg-quick: preliminary support for go implementation
c454c26 allowedips: simplify arithmetic
71d44be allowedips: produce better assembly with unsigned arithmetic
5e3532e allowedips: use native endian on lookup
856f105 allowedips: add selftest for allowedips_walk_by_peer
41df6d2 embeddable-wg-library: zero attribute padding
9a1bea6 keygen-html: add zip file example
f182b1a qemu: retry on 404 in wget for kernel.org race

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