fix #H8481 - placing monster at <0,0>

mon_arrive() -> m_into_limbo() -> migrate_to_level() -> wormgone()
followed by place_monster() "for relmon".  relmon() was changed (last
November, cc5bb44a9a) to not require
the monster be on the map, so just get rid of the place_monster() that
was trying to put the "gone" long worm at <0,0>.

Also, another m_into_limbo() bit:  make mdrop_special_objs() check the
location and send any dropped items to random locations if the monster
dropping things isn't on the map, instead of placing them at <0,0>.

doc/fixes36.2

@@ -1,4 +1,4 @@
-$NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.298 $ $NHDT-Date: 1554425733 2019/04/05 00:55:33 $
+$NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.299 $ $NHDT-Date: 1554580624 2019/04/06 19:57:04 $
 
 This fixes36.2 file is here to capture information about updates in the 3.6.x
 lineage following the release of 3.6.1 in April 2018. Please note, however,
@@ -406,6 +406,9 @@ shorten the getpos prompt for teleport destination so that it won't yield a
 once a status highlight for a temporary rule ('up', 'down', 'changed') timed
 	out, further spurious status updates (evaluating all fields) would
 	occur every 'statushilites' turns even if no fields had changed
+if a migrating long worm couldn't be placed, or some other monster was given
+	an existing long worm's place and it couldn't be put somewhere else,
+	a "trying to place monster at <0,0>" warning would occur
 
 
 Fixes to Post-3.6.1 Problems that Were Exposed Via git Repository

src/dog.c

@@ -1,4 +1,4 @@
-/* NetHack 3.6	dog.c	$NHDT-Date: 1543052701 2018/11/24 09:45:01 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.84 $ */
+/* NetHack 3.6	dog.c	$NHDT-Date: 1554580624 2019/04/06 19:57:04 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.85 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2011. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -7,11 +7,6 @@
 
 STATIC_DCL int NDECL(pet_type);
 
-/* cloned from mon.c; used here if mon_arrive() can't place mon */
-#define LEVEL_SPECIFIC_NOCORPSE(mdat) \
-    (Is_rogue_level(&u.uz)            \
-     || (level.flags.graveyard && is_undead(mdat) && rn2(3)))
-
 void
 newedog(mtmp)
 struct monst *mtmp;
@@ -697,7 +692,8 @@ coord *cc;   /* optional destination coordinates */
         /* **** NOTE: worm is truncated to # segs = max wormno size **** */
         num_segs = min(cnt, MAX_NUM_WORMS - 1); /* used below */
         wormgone(mtmp); /* destroys tail and takes head off map */
-        place_monster(mtmp, mtmp->mx, mtmp->my); /* put head back for relmon */
+        /* there used to be a place_monster() here for the relmon() below,
+           but it doesn't require the monster to be on the map anymore */
     }
 
     /* set minvent's obj->no_charge to 0 */

src/mon.c

@@ -1,4 +1,4 @@
-/* NetHack 3.6	mon.c	$NHDT-Date: 1550524562 2019/02/18 21:16:02 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.279 $ */
+/* NetHack 3.6	mon.c	$NHDT-Date: 1554580625 2019/04/06 19:57:05 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.280 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Derek S. Ray, 2015. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -2649,7 +2649,7 @@ boolean move_other; /* make sure mtmp gets to x, y! so move m_at(x, y) */
     xchar newx, newy;
     coord mm;
 
-    if (mtmp->mx == x && mtmp->my == y && m_at(x,y) == mtmp)
+    if (mtmp->mx == x && mtmp->my == y && m_at(x, y) == mtmp)
         return TRUE;
 
     if (move_other && (othermon = m_at(x, y)) != 0) {
@@ -2668,7 +2668,7 @@ boolean move_other; /* make sure mtmp gets to x, y! so move m_at(x, y) */
          */
         if (!enexto(&mm, newx, newy, mtmp->data))
             return FALSE;
-        if (!isok(mm.x,mm.y))
+        if (!isok(mm.x, mm.y))
             return FALSE;
         newx = mm.x;
         newy = mm.y;

src/steal.c

@@ -1,4 +1,4 @@
-/* NetHack 3.6	steal.c	$NHDT-Date: 1496614914 2017/06/04 22:21:54 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.69 $ */
+/* NetHack 3.6	steal.c	$NHDT-Date: 1554580626 2019/04/06 19:57:06 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.72 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2012. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -693,7 +693,17 @@ struct monst *mon;
            for the other roles are not */
         if (obj_resists(obj, 0, 0) || is_quest_artifact(obj)) {
             obj_extract_self(obj);
-            mdrop_obj(mon, obj, FALSE);
+            if (mon->mx) {
+                mdrop_obj(mon, obj, FALSE);
+            } else { /* migrating monster not on map */
+                if (obj->owornmask) {
+                    mon->misc_worn_check &= ~obj->owornmask;
+                    if (obj->owornmask & W_WEP)
+                        setmnotwielded(mon, obj);
+                    obj->owornmask = 0L;
+                }
+                rloco(obj);
+            }
         }
     }
 }