Select channel with "/join #channel"

[jacobrose]

When you're in a lot of channels, it can be hard to find the one you want. You may not even realize you're already in it!

When you're in this situation, entering "/join #channel" can feel frustrating because nothing appears to happen. You might wonder, "Is the server not responding?" No, you just forgot that you were already in that channel.

This patch selects the channel you attempt to /join even if you're already in it, alleviating this frustration and offering an alternative channel-finding mechanism.