Changing gcnhub to use select() instead of threading, which should fix the problems with ssl

[sonicrules1234]

No description provided.

[tari]

A few observations from my end.

• asyncore or asynchat can probably further cut down on the amount of code required, and is probably more efficient when mechanisms like epoll are available.
• Pointing out that my Twisted rewrite exists too, though I ripped out a lot of messy functionality that wasn't in scope at the time I was working on it.