pgsql: Add the notion of REPLICA IDENTITY for a table.

Add the notion of REPLICA IDENTITY for a table.

Pending patches for logical replication will use this to determine
which columns of a tuple ought to be considered as its candidate key.

Andres Freund, with minor, mostly cosmetic adjustments by me

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/07cacba983ef79be4a84fcd0e0ca3b5fcb85dd65

Modified Files
--------------
doc/src/sgml/catalogs.sgml | 24 +++
doc/src/sgml/ref/alter_table.sgml | 19 ++
src/backend/catalog/heap.c | 1 +
src/backend/catalog/index.c | 1 +
src/backend/commands/tablecmds.c | 222 ++++++++++++++++++++++++
src/backend/nodes/copyfuncs.c | 14 ++
src/backend/nodes/equalfuncs.c | 12 ++
src/backend/parser/gram.y | 40 +++++
src/backend/utils/cache/relcache.c | 53 +++++-
src/bin/pg_dump/pg_dump.c | 143 +++++++++++++--
src/bin/pg_dump/pg_dump.h | 2 +
src/bin/psql/describe.c | 58 ++++++-
src/bin/psql/tab-complete.c | 31 +++-
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_class.h | 32 +++-
src/include/catalog/pg_index.h | 16 +-
src/include/nodes/nodes.h | 1 +
src/include/nodes/parsenodes.h | 8 +
src/include/utils/rel.h | 7 +
src/test/regress/expected/replica_identity.out | 183 +++++++++++++++++++
src/test/regress/parallel_schedule | 2 +-
src/test/regress/serial_schedule | 1 +
src/test/regress/sql/replica_identity.sql | 79 +++++++++
23 files changed, 902 insertions(+), 49 deletions(-)