PUBLISH requests are now handled in the same order than received.

That is specifically useful for pua dialoginfo which was generating dialog
info notifications that were handled in the wrong order with that patch.
PUBLISH with older documents were sometimes treated after PUBLISH requests
with newer documents, leading to incoherent states.
The correct document version number is now set in the NOTIFY requests.

There was a locking bug leading to NOTIFY being issued with the same
version number.
Fixed comparison wrt last changes.
Improved debugging message to make it more useful.
Merge pull request #34 from dsandras/bi-presence-fixes

Bi presence fixes

This is a critical fix ensuring the serial processing of the PUBLISHs for the same presentity. Failing to do so may lead to inconsistent state of the presentity, especially with BLF.
This fix is work on progress for 3 week, tested by Damien.