pgsql: Add system view pg_stat_ssl

Add system view pg_stat_ssl

This view shows information about all connections, such as if the
connection is using SSL, which cipher is used, and which client
certificate (if any) is used.

Reviews by Alex Shulgin, Heikki Linnakangas, Andres Freund & Michael Paquier

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/9029f4b37406b21abb7516a2fd5643e0961810f8

Modified Files
--------------
doc/src/sgml/monitoring.sgml          |   77 ++++++++++++++++++++++++
src/backend/catalog/system_views.sql  |   11 ++++
src/backend/libpq/be-secure-openssl.c |  104 +++++++++++++++++++++++++++++++++
src/backend/postmaster/pgstat.c       |   60 +++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c   |   33 ++++++++++-
src/include/catalog/catversion.h      |    2 +-
src/include/catalog/pg_proc.h         |    2 +-
src/include/libpq/libpq-be.h          |    5 ++
src/include/pgstat.h                  |   21 +++++++
src/test/regress/expected/rules.out   |   12 +++-
10 files changed, 320 insertions(+), 7 deletions(-)