pgsql: Get rid of postgres_fdw's assumption that remote type OIDs match

Get rid of postgres_fdw's assumption that remote type OIDs match ours.

The only place we depended on that was in sending numeric type OIDs in
PQexecParams; but we can replace that usage with explicitly casting
each Param symbol in the query string, so that the types are specified
to the remote by name not OID.  This makes no immediate difference but
will be essential if we ever hope to support use of non-builtin types.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/5fd386bb31f9a8ed5058093bc3f8937fdde3dbec

Modified Files
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contrib/postgres_fdw/deparse.c                 |   18 ++++++++++++------
contrib/postgres_fdw/expected/postgres_fdw.out |   12 ++++++------
contrib/postgres_fdw/postgres_fdw.c            |   15 ++++++++++++++-
3 files changed, 32 insertions(+), 13 deletions(-)