Rename getters in conformance with the "Effective Go" styleguide recommendation:
https://golang.org/doc/effective_go.html#Getters

* move constant definitions
* always give the client at least quitTimeout to respond to ping,
  even if registerTimeout or quitTimeout are longer than idleTimeout

* Lower ident timeout to 1.5 seconds, as discussed in #oragono
* Enforce connection limits at the granularity of ipv4 /32's and ipv6 /64's
* Raise the limit on number of new connections to 64 every 10 minutes
  (for the benefit of people behind large IPv4 NATs)

support for PROXY was removed in 43e28e2fef. After discussion,
it's worth keeping around in case of client compatibility issues,
and until /rehash support is more mature.

Specifically, if you joined a channel while someone else was trying to part. the Join method would grab the lock, the Quit method would queue to grab the lock, the Join method would unlock and then try to regrab the lock, and it would get into a situation where nobody would have the lock and everyone would be waiting for it.

This caused weird oddities with clients.