U162 - killing shopkeeper with unpaid thrown objects

While an object is being thrown, it isn't on any list.  This means that
killing a shopkeeper with an unpaid object wouldn't be able to clear the
unpaid bit.  By the time the object lands, the shopkeeper is gone, and then
it's too late.  Added a new global to track a thrown object, set it and later
clear it in throwit(), also clear it as needed in dealloc_obj(), and check
it in setpaid().  It should be possible to use this global to avoid losing
thrown objects during hangup saves as well.  But that can wait.

src/mkobj.c

@@ -16,6 +16,8 @@ STATIC_DCL void FDECL(check_contained, (struct obj *,const char *));
 #endif
 #endif /* OVL1 */
 
+extern struct obj *thrownobj;		/* defined in dothrow.c */
+
 /*#define DEBUG_EFFECTS*/	/* show some messages for debugging */
 
 struct icp {
@@ -1483,6 +1485,8 @@ dealloc_obj(obj)
     if (obj_sheds_light(obj))
 	del_light_source(LS_OBJECT, (genericptr_t) obj);
 
+    if (obj == thrownobj) thrownobj = (struct obj*)0;
+
     free((genericptr_t) obj);
 }