pgsql: Add new pg_walsummary tool.

Add new pg_walsummary tool.

This can dump the contents of the WAL summary files found in
pg_wal/summaries. Normally, this shouldn't really be something anyone
needs to do, but it may be needed for debugging problems with
incremental backup, or could possibly be useful to external tools.

Discussion: http://postgr.es/m/CA+Tgmobvqqj-DW9F7uUzT-cQqs6wcVb-Xhs=w=hzJnXSE-kRGw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ee1bfd168390bc843c6704d16e909692c0a79f27

Modified Files
--------------
doc/src/sgml/ref/allfiles.sgml        |   1 +
doc/src/sgml/ref/pg_walsummary.sgml   | 122 +++++++++++++++
doc/src/sgml/reference.sgml           |   1 +
src/bin/Makefile                      |   1 +
src/bin/meson.build                   |   1 +
src/bin/pg_walsummary/.gitignore      |   1 +
src/bin/pg_walsummary/Makefile        |  48 ++++++
src/bin/pg_walsummary/meson.build     |  30 ++++
src/bin/pg_walsummary/nls.mk          |   6 +
src/bin/pg_walsummary/pg_walsummary.c | 280 ++++++++++++++++++++++++++++++++++
src/bin/pg_walsummary/t/001_basic.pl  |  19 +++
src/bin/pg_walsummary/t/002_blocks.pl |  88 +++++++++++
src/tools/pgindent/typedefs.list      |   2 +
13 files changed, 600 insertions(+)