2.5.17 released October 5, 1999

- cleanup of hash.h
- new function in utils.c: find_origin()
- attack() and find_defense() represent strings with their origins,
  improving the efficiency of the caching strategy.
- backfill depth decreased from 14 to 10
- optimization and a little cleanup in make_worms()
- bugfix in value_move_reasons()
- three initializing functions tidied away from global view