[Rd] pipe(): input to, and output from, a single process

[Greg Minshall]

Gabor, thanks.  yes, managing the two-way communication is always a bit
error-prone, as it depends on the input/output characteristics of the
two ends -- they either match, or deadlock.  it's too bad if polling is
always *required* -- i'd think sometimes a programmer would be happy
blocking, though other times one wants better control over when to
block.  cheers, Greg