pgsql: Add views and functions to monitor hot standby query conflicts

Add views and functions to monitor hot standby query conflicts

Add the view pg_stat_database_conflicts and a column to pg_stat_database,
and the underlying functions to provide the information.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=40d9e94bd7537144d3d379c1fd1264dff5cf4bb2

Modified Files
--------------
doc/src/sgml/high-availability.sgml | 7 ++
doc/src/sgml/monitoring.sgml | 54 ++++++++++++++++++-
src/backend/catalog/system_views.sql | 14 ++++-
src/backend/postmaster/pgstat.c | 69 +++++++++++++++++++++++
src/backend/tcop/postgres.c | 7 ++
src/backend/utils/adt/pgstatfuncs.c | 101 ++++++++++++++++++++++++++++++++++
src/include/catalog/pg_proc.h | 12 ++++
src/include/pgstat.h | 23 +++++++-
src/test/regress/expected/rules.out | 5 +-
9 files changed, 287 insertions(+), 5 deletions(-)