SQL/MED - file_fdw

Hi, hackers,

Attached is a patch that adds file_fdw, FDW which reads records from
files on the server side, as a contrib module.  This patch is based on
"SQL/MED core functionality" patch.

[SQL/MED - core functionality]
http://archives.postgresql.org/pgsql-hackers/2010-11/msg01698.php

File_fdw can be installed with the steps similar to other contrib
modules, and you can create FDW with the script:
    $SHAREDIR/contrib/file_fdw.sql
Note that you need to create file_fdw for each database.

Document for file_fdw is included in the patch, although the contents
might not be enough.

Any comments and questions are welcome.

Regards,
--
Shigeru Hanada