This (1) fixes an issue where signature files supplied on the command
line wouldn't pass through the hooks, and (2) prepares for allowing
hooks to supply the content of a signature file directly.
It accepts "originator" or "responder" states as a way to enforce that
the signature only matches packets in the associated direction.
The "established" state is rejected as an error since it doesn't
have a useful meaning like it does for the "tcp-state" condition.
