- NLITSET is gone.
- NOW-LIT and NOW-DARK are renamed to NOW-LIT? and NOW-DARK?.
- Global HERE-LIT is set by PARSER before each turn and updated when we notice
  the light status changing. Most code references HERE-LIT instead of calling
  SEARCH-FOR-LIGHT, including the CHECK-LIGHT scope stage (which incorrectly
  used to start a nested MAP-SCOPE by calling SEARCH-FOR-LIGHT).
- The INVENTORY scope stage is now before CHECK-LIGHT so the player can turn on
  a carried light source in the dark.

Updated cloak_plus.zil to use the new light code (plus other cleanup). In
particular, its admonishment to set LIGHTBIT on an object after calling NOW-LIT
rather than before is gone.