wireguard: bump to 0.0.20200205

wireguard: bump to 0.0.20200205

* compat: support building for RHEL-8.2
* compat: remove RHEL-7.6 workaround

Bleeding edge RHEL users should be content now (which includes the actual
RedHat employees I've been talking to about getting this into the RHEL kernel
itself). Also, we remove old hacks for versions we no longer support anyway.

* allowedips: remove previously added list item when OOM fail
* noise: reject peers with low order public keys

With this now being upstream, we benefit from increased fuzzing coverage of
the code, uncovering these two bugs.

* netns: ensure non-addition of peers with failed precomputation
* netns: tie socket waiting to target pid

An added test to our test suite for the above and a small fix for high-load CI
scenarios.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>