Kill <channels> in favour of <connect:maxchans> and <oper:maxchans>.

Remove channels/high-join-limit privilege
m_spanningtree Fix routing of unicast messages
m_sajoin Abort and report if the target user is already on the channel

Fixes issue #820 reported by @UselessOper
m_sajoin, m_sapart Support a comma separated list of channels

Issue #818
core_lusers Don't capitalize "local users" and "global users"
Remove WALLCHOPS and WALLVOICES ISUPPORT tokens

These tokens have been deprecated in favour of STATUSMSG for a long time