fix github pull request #161 - scatter()

Fixes #161

Report states that scattering objects might leave a 'pile' glyph when
no longer appropriate.  I didn't try to reproduce that, just took it
on faith.  The fix tried to be too efficient and might have missed
fixing the display if breaks() or ohitmon() destroyed the objects
being scattered and left 'total' at 0.

doc/fixes36.2

@@ -221,6 +221,7 @@ end of game while carrying Schroedinger's Box would reveal cat-or-corpse
 attempting to untrap an adjacent trap while on the edge of--not in--a pit
 	failed due to not being able to reach the floor
 magic trap's deafening roar effect wasn't waking nearby monsters
+scattering of objects might leave source location with wrong thing displayed
 
 
 Fixes to Post-3.6.1 Problems that Were Exposed Via git Repository

src/explode.c

@@ -1,4 +1,4 @@
-/* NetHack 3.6	explode.c	$NHDT-Date: 1522454717 2018/03/31 00:05:17 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.56 $ */
+/* NetHack 3.6	explode.c	$NHDT-Date: 1543101719 2018/11/24 23:21:59 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.59 $ */
 /*      Copyright (C) 1990 by Ken Arromdee */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -616,6 +616,10 @@ struct obj *obj; /* only scatter this obj        */
     struct scatter_chain *schain = (struct scatter_chain *) 0;
     long total = 0L;
 
+    if (individual_object && (obj->ox != sx || obj->oy != sy))
+        impossible("scattered object <%d,%d> not at scatter site <%d,%d>",
+                   obj->ox, obj->oy, sx, sy);
+
     while ((otmp = (individual_object ? obj : level.objects[sx][sy])) != 0) {
         if (otmp->quan > 1L) {
             qtmp = otmp->quan - 1L;
@@ -759,7 +763,7 @@ struct obj *obj; /* only scatter this obj        */
         free((genericptr_t) stmp);
         newsym(x, y);
     }
-
+    newsym(sx, sy);
     return total;
 }