pgsql: Adjust postgres_fdw's search path handling.

Adjust postgres_fdw's search path handling.

Set the remote session's search path to exactly "pg_catalog" at session
start, then schema-qualify only names that aren't in that schema. This
greatly reduces clutter in the generated SQL commands, as seen in the
regression test changes. Per discussion.

Also, rethink use of FirstNormalObjectId as the "built-in object" cutoff
--- FirstBootstrapObjectId is safer, since the former will accept
objects in information_schema for instance.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/6d06049493862f7f6b639035198fc817949723ae

Modified Files
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contrib/postgres_fdw/connection.c | 29 ++++
contrib/postgres_fdw/deparse.c | 101 ++++++++++-----
contrib/postgres_fdw/expected/postgres_fdw.out | 164 ++++++++++++------------
3 files changed, 180 insertions(+), 114 deletions(-)