rem: int user_thread_wait_on_thread(thread_id id, int *uretcode)
add: user_thread_wait_on_thread(thread_id id, int *uretcode)
context: int user_thread_wait_on_thread(thread_id id, int *uretcode){	int retcode;	int rc, rc2;	if((addr)uretcode >= KERNEL_BASE && (addr)uretcode <= KERNEL_TOP)		return ERR_VM_BAD_USER_MEMORY;	rc = thread_wait_on_thread(id, &retcode);	rc2 = user_memcpy(uretcode, &retcode, sizeof(int));	if(rc2 < 0)		return rc2;	return rc;}