Add VOICEREG channel flag to chanserv

[DasBrain]

(Labels: Chanserv Enhancement)

Add a chanflag to chanserv that auto-voices all registered users who join the channel.

Proposed help:

-Q-  +r VOICEREG   Automatically grants voice (+v) on the channel to any registered user who enters,
-Q-                unless they have quiet (+q) chanlev flag.

Rationale:
Delaying the ability to speak in the channel for unregistered people is a good mitigation strategy against the current spam attack.
This can be archived by setting the channel +DM (delay join, reg-only moderated), and auto-voicing anyone who enters with a delay.

Technically, it is not required to voice unregistered users - but this cause envy if only unregistered users are voiced.
Therefore it might be useful to voice anyone who can speak as soon as they enter the channel.
Also, Q can see through +D, making this feature even more useful - as the join and mode change line come together, and are easier to associate in my brain.