Add propagated klines.

Add propagated klines.

A KLINE command without the ON clause now sets a propagated
("global") ban. KLINE commands with the ON clause work as
before.

Propagated klines can only be removed with an UNKLINE command
without the ON clause, and this removes them everywhere.
In fact, they remain in a deactivated state until the latest
expiry ever used for the mask has passed.

Propagated klines are part of the netburst using a new BAN
message and capab. If such a burst has an effect, both the
server name and the original oper are shown in the server
notice.

No checks whatsoever are done on bursted klines at this time.

The system should be extended to XLINE and RESV later.

There is currently no way to list propagated klines,
but TESTLINE works normally.