Patch to fix minor bug and a little clean-up in ikarus.io.ss

[Derick Eddington]

Made tcp-server-socket and tcp-server-socket-nonblocking do:
  - Check validity of port number range, otherwise it gets cast by C
  code and used incorrectly.
  - Use tcp-server-socket/who for better error who reporting.
  - Use io-error instead of die for ikrt_listen error return.

Fix bug in close-tcp-server-socket where the tcp-server's fd field was
not being set to #F. And use io-error instead of die.

Replaced calls to error with calls to die, where appropriate.

[Derick Eddington (derick-eddington)]

The previous patch had a typo. This new one fixes it.