Fix to Windows build problem with the js reference build; replace non-API macro OBJ_GET_CLASS with API-kosher JS_GetClass. (OBJ_GET_CLASS used js_GetSlotWhileLocked, pulled from the set of exported symbols with the recent thread optimization checkin.)

Not part of the Mozilla build.  (Yes, it's a closed tree!)

r=brendan

js/src/js.c

@@ -1126,7 +1126,7 @@ DumpScope(JSContext *cx, JSObject *obj, JSHashEnumerator dump, FILE *fp)
     JSSymbol *sym;
     int i;
 
-    fprintf(fp, "\n%s scope contents:\n", OBJ_GET_CLASS(cx, obj)->name);
+    fprintf(fp, "\n%s scope contents:\n", JS_GetClass(cx, obj)->name);
     scope = OBJ_SCOPE(obj);
     if (!MAP_IS_NATIVE(&scope->map))
 	return;