pgsql: Add tg_updatedcols to TriggerData

Add tg_updatedcols to TriggerData

This allows a trigger function to determine for an UPDATE trigger
which columns were actually updated. This allows some optimizations
in generic trigger functions such as lo_manage and
tsvector_update_trigger.

Reviewed-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Discussion: https://www.postgresql.org/message-id/flat/11c5f156-67a9-0fb5-8200-2a8018eb2e0c(at)2ndquadrant(dot)com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/71d60e2aa05157efec28393b15c0b0b9fc1b210c

Modified Files
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contrib/lo/expected/lo.out | 8 ++++++++
contrib/lo/lo.c | 3 ++-
contrib/lo/sql/lo.sql | 5 +++++
doc/src/sgml/trigger.sgml | 25 +++++++++++++++++++++++++
src/backend/commands/trigger.c | 6 ++++++
src/backend/utils/adt/tsvector_op.c | 29 +++++++++++++++++++++--------
src/include/commands/trigger.h | 1 +
7 files changed, 68 insertions(+), 9 deletions(-)