missile light sources

Throwing or kicking a lit lamp, lit candle, or lit potion of oil
wasn't giving off any light as it travelled to its destination.
Now it does, and dungeon features, objects, or monsters that are
temporarily seen as it moves from square to square till appear on
the map.  In the monster case, they go away as soon as the light
moves beyond range, but when it finishes moving the "remembered,
unseen monster" glyph will be drawn at their location.  I think that
part has some room for improvement, but mapping temporarily seen
terrain features is the primary impetus for this change.

Also, any message delivery while the "lit missile" travelled still
showed its light around the hero.  Noticeable for lamps or stacks
of sufficient candles if hero has no other light source.

This cannibalizes the monst->mburied bit for temporarily seeing a
monster.  It has been present but unused for ages.  I needed to
replace a couple of vision macros to make sure they didn't examine
it any more so that overloading for transient lighting doesn't
introduce any vision oddities.  For version $NEXT, monst->mtemplit
can be given its own bit.  It is only set during bhit() execution
and cleared by the time that returns, so has no effect on save files.

src/save.c

@@ -1,4 +1,4 @@
-/* NetHack 3.6	save.c	$NHDT-Date: 1558880688 2019/05/26 14:24:48 $  $NHDT-Branch: NetHack-3.6 $:$NHDT-Revision: 1.120 $ */
+/* NetHack 3.6	save.c	$NHDT-Date: 1559994625 2019/06/08 11:50:25 $  $NHDT-Branch: NetHack-3.6 $:$NHDT-Revision: 1.121 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Michael Allison, 2009. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -1078,6 +1078,8 @@ struct monst *mtmp;
 {
     int buflen;
 
+    mtmp->mtemplit = 0; /* normally clear; if set here then a panic save
+                         * is being written while bhit() was executing */
     buflen = (int) sizeof (struct monst);
     bwrite(fd, (genericptr_t) &buflen, sizeof buflen);
     bwrite(fd, (genericptr_t) mtmp, buflen);