Use *init* and *cleanup* in existing actors.

* 8sync/repl.scm (<repl-manager>):
* 8sync/systems/irc.scm (<irc-bot>): Switch from an 'init action to the
implicit '*init* action.

* 8sync/systems/irc.scm (<irc-bot>, irc-bot-cleanup): Add *cleanup*
handler.

* demos/ircbot.scm:
* doc/8sync-new-manual.org: Drop some calls to 'init when
bootstrapping-messages since we now use '*init*.