object deletion bookkeeping

After the apply-wielded-pie-to-blind-self (quite a while back) and
quivered-candle-burns-out (a week or two ago) bugs where object deletion
left dangling worn-object pointers, add a general check to try to catch
such things at the time of deletion.  Also, clear thrownobj and kickobj
pointers at the time corresponding object is deleted.  (This doesn't add
any checks for them becoming null during process of throwing or kicking,
where I'm not sure that the possibility of missile going away is being
adequately tracked).

src/shk.c

@@ -27,6 +27,7 @@ STATIC_DCL void FDECL(kops_gone, (BOOLEAN_P));
 
 extern const struct shclass shtypes[];	/* defined in shknam.c */
 extern struct obj *thrownobj;		/* defined in dothrow.c */
+extern struct obj *kickobj;		/* dokick.c */
 
 STATIC_VAR NEARDATA long int followmsg;	/* last time of follow message */
 STATIC_VAR const char and_its_contents[] = " and its contents";
@@ -279,6 +280,7 @@ register struct monst *shkp;
 	clear_unpaid(fobj);
 	clear_unpaid(level.buriedobjlist);
 	if (thrownobj) thrownobj->unpaid = 0;
+	if (kickobj) kickobj->unpaid = 0;
 	for(mtmp = fmon; mtmp; mtmp = mtmp->nmon)
 		clear_unpaid(mtmp->minvent);
 	for(mtmp = migrating_mons; mtmp; mtmp = mtmp->nmon)
@@ -847,6 +849,16 @@ register struct obj *obj, *merge;
 #endif
 		}
 	}
+	if (obj->owornmask) {
+	    impossible("obfree: deleting worn obj (%d: %ld)",
+		       obj->otyp, obj->owornmask);
+	    /* unfortunately at this point we don't know whether worn mask
+	       applied to hero or a monster or perhaps something bogus, so
+	       can't call remove_worn_item() to get <X>_off() side-effects */
+	    setnotworn(obj);
+	}
+	if (obj == thrownobj) thrownobj = 0;
+	if (obj == kickobj) kickobj = 0;
 	dealloc_obj(obj);
 }