DOCUMENTATION:

I: Jingle
Jingle is a module who can't work alone. His meaning of life is make working
others modules. There is two sorts of modules: applications (File Transfer, Voice)
and transports (IBB, socks5, ...).
The "sub-modules" must register in jingle and provide some generic function.
After the jingle module catch and dispatch all jingle's iqs. And offer an
interface between apps and trans.
Jingle module keep a way of all sessions via JingleSession structures.
This JingleSession got all the informations and a list of SessionContent, which
are struct containing information about content and 2 gconstpointer. This pointer
are data from apps and trans.

An application module must provide:
- check: check if the description of a JingleContent is correct;
- handle: each application have some options not conventional, so handle is the
          less option. We give him all the jingle iqs than other function doesn't
          handle;
- tomessage: add the gconstpointer to a given node;
- handle_data: when the peer send data to us, the trans module catch it and
               give it to jingle. After jingle give it to the apps via this
               function;
- start: the session have been accepted we can init our transfer;
- send: it's call until there is datas to send;
- stop: we've got a session-terminate, we need to close transfer, files, ...

An transport module must provide:
- check: the same as application;
- tomessage: idem;
- cmp: to know if 2 transports are the same. Use by IBB, when we got
       a new data jingle must look the gconstpointer to got the ibb-id to know
       which apps is concerned;
- xmlns: util when we got only funcs, to know who are we;
- new: to create a new transport node, with default options;
-send: to send data given by apps via jingle.