SocketHandler has been renamed to TCPSocketHandler
SocketHandler is now a simple interface with a few methods, used only by
Poller.

This way we can inherite from the new SocketHandler class, to handle other
types of sockets, and still make them manageable by the poller without any
change in the Poller class.

fix #2551

fix #2552

See CMP0037

Was causing the event to not be removed in case of connection failure, which
lead to a dangling timed event named “timeout-1”, which was called later, by
some other SocketHandler for which even the socket creation failed (so, its
socket is -1), with a pointer to the previous SocketHandler which has
disappeared for a long time: segmentation fault etc.

ref #2455

A result or an error, depending on the type of message

This actually makes the session_manager be useful, and saves a few octets of
memory for the other ones

For example, both JID #chan%server@biboumi/Toto and toto!server@biboumi are
equivalent, except that if you send a message to the first one, subsequent
messages coming from the user toto will come from that same JID. This is
done to be consistent for the XMPP user, and respond from the same JID than
the 'to' of the first message.

fix #2468

IRC users and channels are now distinguished by the separator used in the
IID (% or !).

ref #2468

ref #2521

ref #2521

fix #2541