[Verse-dev] fixing session_get_size

[Brecht Van Lommel]

Hi,

I fixed a bug that would sometimes keep the client/server from sending
acks/naks. As a result of this the history buffer didn't get cleared. As
a result of this, verse_session_get_size() now works.

Acks/naks are still counted though, so you can expect it to return
values up to around ~10 when everything has been sent. This should make
writing data pushers easier, since they only need to check if this
function once all layers are created.

Cheers,
Brecht.