Little documentation update

Rename cmake target test->test_suite for cmake 3.0

See CMP0037

Delete the timeout event using the correct socket number, instead of -1

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.

Support version request to IRC users

Respond to IQ version on the gateway, a server or a chan with biboumi version

ref #2455

Write the software version, including the git hash, in config.h using cmake

Return a proper iq when the IRC server responds to our kick

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

Implement a way to add callbacks, waiting for an IRC event to return an iq

Remove a duplicate “connection closed” message

Make the Botan rng, credential_manager etc be static

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

Document the new way to send private messages

Messages to room participants are forwarded to the IRC user

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

Mini comment fix

includes from cmake BINARY_DIR should be included before considering SOURCE_DIR

Document the encryption, and a few documentation issues are fixed

Rewrite the whole IID usage

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

ref #2468

Add an <error/> element when the provided form is wrong, in two ad-hoc commands

Handle the 'cancel' ad-hoc action, and return an error for unsupported actions

ref #2521

Remove inactive ad-hoc sessions after a given time

ref #2521

Make the XMPP component port configurable

fix #2541