pgsql: Add pg_promote function

Add pg_promote function

This function is able to promote a standby with this new SQL-callable
function.  Execution access can be granted to non-superusers so that
failover tools can observe the principle of least privilege.

Catalog version is bumped.

Author: Laurenz Albe
Reviewed-by: Michael Paquier, Masahiko Sawada
Discussion: https://postgr.es/m/6e7c79b3ec916cf49742fb8849ed17cd87aed620.camel@cybertec.at

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/10074651e3355e2405015f6253602be8344bc829

Modified Files
--------------
doc/src/sgml/func.sgml                     | 19 ++++++++
doc/src/sgml/high-availability.sgml        | 19 ++++----
doc/src/sgml/monitoring.sgml               |  6 ++-
doc/src/sgml/recovery-config.sgml          |  3 +-
src/backend/access/transam/xlog.c          |  6 ---
src/backend/access/transam/xlogfuncs.c     | 77 ++++++++++++++++++++++++++++++
src/backend/catalog/system_views.sql       |  6 +++
src/backend/postmaster/pgstat.c            |  3 ++
src/include/access/xlog.h                  |  6 +++
src/include/catalog/catversion.h           |  2 +-
src/include/catalog/pg_proc.dat            |  4 ++
src/include/pgstat.h                       |  1 +
src/test/recovery/t/004_timeline_switch.pl | 11 +++--
13 files changed, 143 insertions(+), 20 deletions(-)