Ticket 223: Converting current-{input,output}-ports to binary

The standard input and output ports which current-input-port and current-output-port are initially bound to are not opened explicitly. They default to character ports. Should they be replaceable with equivalent binary ports using the following procedures?

• (standard-input-is-binary!)
• (standard-output-is-binary!)

It is an error to call either of these if the corresponding current-{input,output}-port is not the original value, or if any I/O has been performed on them, or if they cannot reasonably be treated as binary.