Map irc commands to callbacks, in a clean way

Basic handling of modes, both ways

Read the served hostname from the config file

Unescape XML before sending messages over IRC

Handle nick changes, both ways

Add a Config module, and use it to get the password from a file

Handle private messages, both ways

Handle the ACTION (/me) IRC command, both ways

Connect to localhost instead of the served hostname

Because the XMPP component connection is only available locally, the XMPP
servers proably only listen on 127.0.0.1 instead of 0.0.0.0.

Handle IRC QUIT command

Fix the include of the config.h

And actually use the values found by cmake

Properly detect iconv features to compile

Add include for perror

Use the Expat library directly instead of relying on expatpp

And now we handle namespaces, yay.
And a nice little test.

Aaaand, I forgot to add files

Implement part and join, both ways

Remove IRC colors from the body when forwarding it to XMPP

Cosmetic

Check UTF-8 encoding, and convert strings to UTF-8

Handle conversion errors properly by inserting � instead.  Add a binary
header to provide portable way to write binary literals (I like them) Also
add a test file.  ref #2404