libxt_policy: option table fixes, improved error tracking

Most of the flags are multi-use in this extension. Also transfer
--next => --strict requirement to option table.

Furthermore, augment the error messages emitted from fcheck to contain
the policy element number, and elaborate on what an "empty policy
element" is.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
2 files changed