The sync.atomic documentation says:

"On both ARM and x86-32, it is the caller's responsibility to arrange
for 64-bit alignment of 64-bit words accessed atomically."

fix #214

nickserv: implement GHOST, GROUP, DROP, and INFO

Sequence of events:

1. client.nickTimer.Stop()
2. client.server.accounts.Logout(client)
3. accounts sees that client is no longer logged in, does client.nickTimer.Touch()
4. 30 seconds later, RandomlyRename resurrects the zombie client

add an option to expose a pprof http endpoint

fix #204

Empty channels were only cleaned up on PART, not QUIT.

two nickname reservation fixes

implement #199

some small fixes

"There is no error reply for bad channel names."
<https://tools.ietf.org/html/rfc2812#section-3.2.5>

See #197 (this is not a complete fix, though).

implement mailto callbacks

clean up stopEvent (requires go v1.10)

fix #192

changes to nick reservation

* Clients are now renamed, not disconnected, on reservation timeout
* Nick reservation config is now its own subsection