2.7.153 released August 13, 2000

- autohelper vitality() removed
- autohelper weak() revised
- struct dragon_data field safety renamed old_safety
- new field invincible in struct worm_data
- dragon_invincible() in dragon.c implemented
- worm invincibility and dragon safety printed in show_dragons()
- dragon safety values revised
- init_influence() revised
- connection_value2() in move_reasons.c reimplemented and renamed
  connection_value()
- dragon status used instead of dragon safety in showbord.c