[project @ 1999-09-16 13:14:38 by simonmar]

Cleanup of non-blocking I/O

- file descriptors are now always set to non-blocking mode.

- we don't do an inputReady operation on descriptors before
  attempting to read from them any more.

- the non-blocking flag on Handles has gone.

- the {set,clear}[Conn]NonBlockingFlag() functions have gone.

- the socket operations have been made to work properly with threads:
  accept is now non-blocking (it does a threadWaitRead instead of
  blocking), and the file descriptors returned by accept are set to
  non-blocking mode.

Win32 will need some adjustments, no doubt.