update vm for startup branch

vm/factor.cpp

@@ -174,7 +174,7 @@ void factor_vm::start_factor(vm_parameters *p)
 void factor_vm::stop_factor()
 {
 	nest_stacks(NULL);
-	c_to_factor_toplevel(userenv[SHUTDOWN_ENV]);
+	c_to_factor_toplevel(special_objects[OBJ_SHUTDOWN]);
 	unnest_stacks();
 }
 

vm/objects.hpp

@@ -34,6 +34,7 @@ enum special_object {
 
 	OBJ_BOOT            = 20, /* boot quotation */
 	OBJ_GLOBAL,               /* global namespace */
+	OBJ_SHUTDOWN,
 
 	/* Quotation compilation in quotations.c */
 	JIT_PROLOG          = 23,