flush the write buffer and/or fill the read buffer.
Use the BIO_ctrl_pending(), to find out whether data is buffered in the BIO
-and must be transfered to the network. Use BIO_ctrl_get_read_request() to
+and must be transferred to the network. Use BIO_ctrl_get_read_request() to
find out, how many bytes must be written into the buffer before the
SSL_operation() can successfully be continued.