m_spanningtree Bump protocol version and remove unused CAPAB CAPABILITIES entries
m_spanningtree Introduce IJOIN and RESYNC

When a local user joins an existing channel, instead of an FJOIN, send an IJOIN with the channel name being the first parameter.
If the joining user received prefix modes, append the channel TS and the prefix mode letters as the second and third parameters.

When receiving an IJOIN, first check if the target channel exists. If it does not exist, ignore the join (that is, do not create the channel) and send a RESYNC back to the source.

If the channel does exist then join the user, and in case any prefix modes were sent (found in the 3rd parameter), compare the TS of the channel to the TS in the IJOIN (2nd parameter).
If the timestamps match, set the modes on the user, otherwise ignore the modes.

Outgoing IJOINs to 1202 protocol servers are converted to FJOINs, but the channel mode parameter is left empty ("+").