pgsql: Add GUC ignore_invalid_pages.

Add GUC ignore_invalid_pages.

Detection of WAL records having references to invalid pages
during recovery causes PostgreSQL to raise a PANIC-level error,
aborting the recovery. Setting ignore_invalid_pages to on causes
the system to ignore those WAL records (but still report a warning),
and continue recovery. This behavior may cause crashes, data loss,
propagate or hide corruption, or other serious problems.
However, it may allow you to get past the PANIC-level error,
to finish the recovery, and to cause the server to start up.

Author: Fujii Masao
Reviewed-by: Michael Paquier
Discussion: https://www.postgresql.org/message-id/CAHGQGwHCK6f77yeZD4MHOnN+PaTf6XiJfEB+Ce7SksSHjeAWtg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/41c184bc642b25f67fb1d8ee290f28805fa5a0b4

Modified Files
--------------
doc/src/sgml/config.sgml               | 25 +++++++++++++++++++++++++
src/backend/access/transam/xlogutils.c |  9 +++++++--
src/backend/utils/misc/guc.c           | 20 ++++++++++++++++++++
3 files changed, 52 insertions(+), 2 deletions(-)