BIO_ctrl(b,BIO_CTRL_POP,0,NULL);
BIO *BIO_pop(BIO *b)	{	BIO *ret;	if (b == NULL) return(NULL);	ret=b->next_bio;	if (b->prev_bio != NULL)		b->prev_bio->next_bio=b->next_bio;	if (b->next_bio != NULL)		b->next_bio->prev_bio=b->prev_bio;	b->next_bio=NULL;	b->prev_bio=NULL;	BIO_ctrl(b,BIO_CTRL_POP,0,NULL);	return(ret);	}