From: Magnus Hagander <mha@sollentuna.net>

Here is a first patch to cleanup the backend side of libpq.
This patch removes all external dependencies on the "Pfin" and "Pfout" that
are declared in pqcomm.h. These variables are also changed to "static" to
make sure.
Almost all the change is in the handler of the "copy" command - most other
areas of the backend already used the correct functions.
This change will make the way for cleanup of the internal stuff there - now
that all the functions accessing the file descriptors are confined to a
single directory.