battle_calcs: remove an accidentally committed line
Fred zone holding: reduce village bonus for regenerating units

It’s still a pretty large bonus as we want to block villages from the
enemy, but shouldn’t be as high as for non-regenerating units, so that
the latter are preferred.
Fred zone advancing: don't force move to village for slightly injured units

The cutoff of 12 HP less than max is arbitrary at this time, to be
refined later.
Fred high priority attack: fix variable names bug
Fred attack eval: use the new attack rating mechanism in battle_calcs

Don’t do a similar but separate evaluation here.
Fred attack eval: adjust poisoner rating to new rating system
Fred attack rating: discourage attacks from hexes adjacent to unoccupied villages
Fred: don't do separate trapping attack evaluation

Instead, use the standard evaluation and give a bonus if it is a
trapping attack.
Fred zone holding: adjust HP ratios for the main zones
Fred: tweak some debug messages