The copyright and license notice is already in the LICENSE file. There
is no justifiable reason to also require that it be included in every
file, since the individual files are not individually distributed except
as part of the entire package.
a) create a layer of indirection in net.Stream to allow swapping in
different read/write implementations and
b) emit an 'fd' event when file descriptors are received over a UNIX pipe,
as finally as a tangential benefit
c) remove a bunch of conditionals from the primary codepaths for
ease-of-reading.
