wireguard: bump to version 0.0.20180420
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 062dcceed0ba0d2b1929597ad9b0393dbdb21628)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>