Make CHANTYPES handling somewhat sane.

Get rid of weird round-the-houses method of processing, and avoid
duplicating the value in a map and a field.

This fixes our handling of servers doing really stupid, theoretical
things like resetting the CHANTYPES they support. (And by "fixes"
I mean the parser will keep state, while everything else burns
around it.)

Change-Id: Ie4936f21e68e4bb1134e9be3f16932eef4ab086f
Reviewed-on: http://gerrit.dmdirc.com/2831
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Shane Mc Cormack <shane@dmdirc.com>