[PATCH] COPY .. COMPRESSED

Greetings,

Attached is a patch to add a 'COMPRESSED' option to COPY which will
cause COPY to expect a gzip'd file on input and which will output a
gzip'd file on output. Included is support for backend COPY, psql's
\copy, regression tests for both, and documentation.

On top of this I plan to submit a trivial patch to add support for
this to file_fdw, allowing creation of FDW tables which operate
directly on compressed files (including CSVs, which is what I need
this patch for).

I've also begun working on a patch to allow this capability to be used
through pg_dump/pg_restore which would reduce the bandwidth used
between the client and the server for backups and restores. Ideally,
one would also be able to use custom format dumps, with compression,
even if the client-side pg_dump/pg_restore wasn't compiled with zlib
support.

Thanks,

Stephen