pgsql: Add a relkind field to RangeTblEntry to avoid some syscache look

Add a relkind field to RangeTblEntry to avoid some syscache lookups.

The recent additions for FDW support required checking foreign-table-ness
in several places in the parse/plan chain. While it's not clear whether
that would really result in a noticeable slowdown, it seems best to avoid
any performance risk by keeping a copy of the relation's relkind in
RangeTblEntry. That might have some other uses later, anyway.
Per discussion.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/bdca82f44d0e0168dece56cbd53b54ba142f328f

Modified Files
--------------
src/backend/catalog/dependency.c | 1 +
src/backend/commands/copy.c | 1 +
src/backend/nodes/copyfuncs.c | 1 +
src/backend/nodes/equalfuncs.c | 1 +
src/backend/nodes/nodeFuncs.c | 2 -
src/backend/nodes/outfuncs.c | 2 +-
src/backend/nodes/print.c | 8 +---
src/backend/nodes/readfuncs.c | 2 +-
src/backend/optimizer/path/allpaths.c | 67 +++++++++++++++++----------------
src/backend/optimizer/plan/planner.c | 3 +-
src/backend/parser/analyze.c | 23 +++--------
src/backend/parser/parse_relation.c | 2 +
src/backend/parser/parse_target.c | 2 -
src/backend/rewrite/rewriteHandler.c | 9 ++++-
src/backend/utils/adt/ri_triggers.c | 2 +
src/backend/utils/adt/ruleutils.c | 7 +++-
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_class.h | 17 ++++----
src/include/nodes/parsenodes.h | 7 ++-
19 files changed, 85 insertions(+), 74 deletions(-)