no_charge items sanity - shop theft

More unpaid/no_charge sanity checking.  If a shop contained any
no_charge objects and was robbed, they would be left no_charge and
trigger sanity check warnings (no_charge in "untended shop") once
the shopkeeper got past any Kops in the way and exited the shop.
Earlier testing didn't wait around long enough for that exit to
happen.

Clear no_charge as soon as the robbery is detected.

src/shk.c

@@ -215,7 +215,7 @@ shkgone(struct monst* mtmp)
 }
 
 void
-set_residency(register struct monst* shkp, register boolean zero_out)
+set_residency(struct monst *shkp, boolean zero_out)
 {
     if (on_level(&(ESHK(shkp)->shoplevel), &u.uz))
         gr.rooms[ESHK(shkp)->shoproom - ROOMOFFSET].resident =
@@ -223,7 +223,7 @@ set_residency(register struct monst* shkp, register boolean zero_out)
 }
 
 void
-replshk(register struct monst* mtmp, register struct monst* mtmp2)
+replshk(struct monst *mtmp, struct monst *mtmp2)
 {
     gr.rooms[ESHK(mtmp2)->shoproom - ROOMOFFSET].resident = mtmp2;
     if (inhishop(mtmp) && *u.ushops == ESHK(mtmp)->shoproom) {
@@ -250,7 +250,7 @@ restshk(struct monst* shkp, boolean ghostly)
     }
 }
 
-/* Clear the unpaid bit on a single object and its contents. */
+/* Clear the unpaid and no_charge bits on a single object and its contents. */
 static void
 clear_unpaid_obj(struct monst *shkp, struct obj *otmp)
 {
@@ -258,6 +258,41 @@ clear_unpaid_obj(struct monst* shkp, struct obj* otmp)
         clear_unpaid(shkp, otmp->cobj);
     if (onbill(otmp, shkp, TRUE))
         otmp->unpaid = 0;
+
+    if (otmp->no_charge) {
+        struct monst *rm_shkp;
+        int rno;
+        coordxy x, y;
+
+        /*
+         * Clear no_charge if
+         *  not located somewhere that we expect no_charge (which is
+         *    floor [of shop] or inside container [on shop floor])
+         *  or can't find object's map coordinates (should never happen
+         *    for floor or contained; conceivable if on shop bill somehow
+         *    but would have failed the floor-or-contained test since
+         *    containers get emptied before going onto bill)
+         *  or fails location sanity check (should always be good when
+         *    location successfully found)
+         *  or not inside any room
+         *  or the room isn't a shop
+         *  or the shop has no shopkeeper (deserted)
+         *  or shopkeeper is the current one (to avoid clearing no_charge
+         *    for items located in some rival's shop).
+         *
+         * no_charge items in a shop which is only temporarily deserted
+         * become owned by the shop now and will be for-sale once the shk
+         * returns.
+         */
+        if ((otmp->where != OBJ_FLOOR && otmp->where != OBJ_CONTAINED)
+            || !get_obj_location(otmp, &x, &y, OBJ_CONTAINED | OBJ_BURIED)
+            || !isok(x, y)
+            || (rno = levl[x][y].roomno) < ROOMOFFSET
+            || !IS_SHOP(rno - ROOMOFFSET)
+            || (rm_shkp = gr.rooms[rno - ROOMOFFSET].resident) == 0
+            || rm_shkp == shkp)
+            otmp->no_charge = 0;
+    }
 }
 
 /* Clear the unpaid bit on all of the objects in the list. */
@@ -302,11 +337,11 @@ setpaid(register struct monst* shkp)
 }
 
 static long
-addupbill(register struct monst* shkp)
+addupbill(struct monst *shkp)
 {
-    register int ct = ESHK(shkp)->billct;
+    int ct = ESHK(shkp)->billct;
-    register struct bill_x *bp = ESHK(shkp)->bill_p;
+    struct bill_x *bp = ESHK(shkp)->bill_p;
-    register long total = 0L;
+    long total = 0L;
 
     while (ct--) {
         total += bp->price * bp->bquan;
@@ -316,10 +351,10 @@ addupbill(register struct monst* shkp)
 }
 
 static void
-call_kops(register struct monst* shkp, register boolean nearshop)
+call_kops(struct monst *shkp, boolean nearshop)
 {
     /* Keystone Kops srt@ucla */
-    register boolean nokops;
+    boolean nokops;
 
     if (!shkp)
         return;
@@ -373,9 +408,9 @@ call_kops(register struct monst* shkp, register boolean nearshop)
 
 /* x,y is strictly inside shop */
 char
-inside_shop(register coordxy x, register coordxy y)
+inside_shop(coordxy x, coordxy y)
 {
-    register char rno;
+    char rno;
 
     rno = levl[x][y].roomno;
     if ((rno < ROOMOFFSET) || levl[x][y].edge || !IS_SHOP(rno - ROOMOFFSET))