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(-)