Utility handling of auto-tagging and tracking TH on mobs.
Limit breadcrumb messages to those that aren't just the base sets.action.
Rewrite target change code to improve and simplify it.  Requires tracking
last known target.
Put 'Engaged' filter in TH_for_first_hit.  Remove filter from th_update.
Tweak for better message reporting, and locking/unlocking, during first hit.
Update comment on handling self-command.
Remove wait in send_command.
Only unlock/message state change of 'None' when gear is currently locked.