Add a basic XMPP component implementation, doing the authentication

Add an XmppParser, and Stanza classes

Generate events on stanza and stream open/close.
Create Stanza and serialize them.

Note: XML namespaces are not handled yet.

Rename libirc and libxmpp to irc and xmpp

Add initial CMakeLists.txt that compiles the current code

Move the basic socket implementation into the SocketHandler class

(that is, the read/write/connect/etc)
Because this code is actually common for both the IrcClient and
XmppComponent class. These two classes have to implement some higher level
callbacks (parsing the data provided in the buffers, doing stuff when the
connection is done) instead of doing the read/write/connect low level
things.

Add irc_message.hpp

Basic IRC message parsing/sending

Add some dummy main

First step of the connection skeleton

Basic connect, socket creating, polling, recving, etc.