[pgpool-committers: 6960] pgpool: Add new show command "show pool_backend_stats".

[Tatsuo Ishii]

Add new show command "show pool_backend_stats".

The new command shows the number SQL commands executed since Pgpool-II
started.

Discussion: https://www.pgpool.net/pipermail/pgpool-hackers/2020-July/003754.html

Branch
------
master

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=689a8fccdee4e91fea0f5a79b5757032e9d7ce1e

Modified Files
--------------
doc/src/sgml/ref/allfiles.sgml                |  1 +
doc/src/sgml/ref/show_pool_backend_stats.sgml | 63 +++++++++++++++++++
doc/src/sgml/reference.sgml                   |  1 +
src/include/pcp/libpcp_ext.h                  | 16 +++++
src/include/utils/pool_process_reporting.h    |  5 +-
src/protocol/pool_proto_modules.c             | 10 +++
src/utils/pool_process_reporting.c            | 88 +++++++++++++++++++++++++++
7 files changed, 183 insertions(+), 1 deletion(-)