[Vortex] doc+api comments on vortex_connection_new and vortex_channel_new

[Sam Roberts]

Hi Francis,

Doc comment:

They don't return a connection or channel object if the on_connected or
on_channel_created callbacks are provided. I hadn't realized this from
reading the docs, its kindof implied, but not outright stated!

API comment:

VortexOnCloseChannel ... must return true/false, so is not so useful
if you have to post it's result to a new thread, where the decision to
allow close or not will be made.

Can it NOT return? Will that block other threads?

Cheers,
Sam