pgsql: Revert "Allow on-line enabling and disabling of data checksums"

Revert "Allow on-line enabling and disabling of data checksums"

This reverts the backend sides of commit 1fde38beaa0c3e66c340efc7cc0dc272d6254bb0.
I have, at least for now, left the pg_verify_checksums tool in place, as
this tool can be very valuable without the rest of the patch as well,
and since it's a read-only tool that only runs when the cluster is down
it should be a lot safer.

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/a228cc13aeabff308d6dfc98a1015865f5393fce

Modified Files
--------------
doc/src/sgml/func.sgml | 65 --
doc/src/sgml/ref/initdb.sgml | 6 +-
doc/src/sgml/reference.sgml | 1 -
doc/src/sgml/wal.sgml | 81 --
src/backend/access/rmgrdesc/xlogdesc.c | 16 -
src/backend/access/transam/xlog.c | 124 +---
src/backend/access/transam/xlogfuncs.c | 59 --
src/backend/catalog/system_views.sql | 5 -
src/backend/postmaster/Makefile | 5 +-
src/backend/postmaster/bgworker.c | 7 -
src/backend/postmaster/checksumhelper.c | 855 ----------------------
src/backend/postmaster/pgstat.c | 5 -
src/backend/replication/basebackup.c | 2 +-
src/backend/replication/logical/decode.c | 1 -
src/backend/storage/ipc/ipci.c | 2 -
src/backend/storage/page/README | 3 +-
src/backend/storage/page/bufpage.c | 6 +-
src/backend/utils/misc/guc.c | 37 +-
src/bin/pg_upgrade/controldata.c | 9 -
src/bin/pg_upgrade/pg_upgrade.h | 2 +-
src/bin/pg_verify_checksums/pg_verify_checksums.c | 5 +-
src/include/access/xlog.h | 10 +-
src/include/access/xlog_internal.h | 7 -
src/include/catalog/pg_control.h | 1 -
src/include/catalog/pg_proc.dat | 8 -
src/include/pgstat.h | 4 +-
src/include/postmaster/checksumhelper.h | 31 -
src/include/storage/bufpage.h | 1 -
src/include/storage/checksum.h | 7 -
src/test/Makefile | 3 +-
src/test/checksum/.gitignore | 2 -
src/test/checksum/Makefile | 24 -
src/test/checksum/README | 22 -
src/test/checksum/t/001_standby_checksum.pl | 101 ---
src/test/isolation/expected/checksum_cancel.out | 27 -
src/test/isolation/expected/checksum_enable.out | 27 -
src/test/isolation/isolation_schedule | 4 -
src/test/isolation/specs/checksum_cancel.spec | 47 --
src/test/isolation/specs/checksum_enable.spec | 70 --
39 files changed, 34 insertions(+), 1658 deletions(-)