wireguard: bump to 0.0.20180802

wireguard: bump to 0.0.20180802

Changelog taken from the version announcement
>
> == Changes ==
>
>   * chacha20poly1305: selftest: split up test vector constants
>
>   The test vectors are encoded as long strings -- really long strings -- and
>   apparently RFC821 doesn't like lines longer than 998.
>   https://cr.yp.to/smtp/message.html
>
>   * queueing: keep reference to peer after setting atomic state bit
>
>   This fixes a regression introduced when preparing the LKML submission.
>
>   * allowedips: prevent double read in kref
>   * allowedips: avoid window of disappeared peer
>   * hashtables: document immediate zeroing semantics
>   * peer: ensure resources are freed when creation fails
>   * queueing: document double-adding and reference conditions
>   * queueing: ensure strictly ordered loads and stores
>   * cookie: returned keypair might disappear if rcu lock not held
>   * noise: free peer references on failure
>   * peer: ensure destruction doesn't race
>
>   Various fixes, as well as lots of code comment documentation, for a
>   small variety of the less obvious aspects of object lifecycles,
>   focused on correctness.
>
>   * allowedips: free root inside of RCU callback
>   * allowedips: use different macro names so as to avoid confusion
>
>   These incorporate two suggestions from LKML.
>
> This snapshot contains commits from: Jason A. Donenfeld and Jann Horn.

Taken from upstream commit : 68e2ebe64a0f27eb25c0e56ef1125ce1318e2279