Private messages within the channel context

In order to escape the target flood limit, it will be allowed to send an
arbitrary number of private messages to users who are on the same channel. In
order to disallow spam, this privilege is only granted to channel ops. Because
it would use too much cpu for the server to check for each private message if two
people are on the same channel, you will have to give the channel context yourself
and as such use a new command: CPRIVMSG (or CNOTICE). The syntax of the
client-server protocol is as follows:

CPRIVMSG <nick> <channel> :<text>

Where <channel> is only used to check if <nick> and the user sending this
message are both on that channel. The idea is that this will benefit channels
where the channel ops are using private message heavily, as is the case on help
channels and certain game channels.