input-port-open? and output-port-open? should not raise an error when port is given

[Takashi Kato]

This raises an error

(output-port-open? (current-input-port))

As long as given paremeter is a port, then this should not raise an error.

[Takashi Kato]

Not raise an error for ports (Fixes #119) input-port-open? and output-port-open? should accept port as its argument. Previous implementations raised an error if it's not input or output port, respectively.

→ <<cset e02d48c14009>>