pgsql: Match pg_user_mappings limits to information_schema.user_mapping

Match pg_user_mappings limits to information_schema.user_mapping_options.

Both views replace the umoptions field with NULL when the user does not
meet qualifications to see it. They used different qualifications, and
pg_user_mappings documented qualifications did not match its implemented
qualifications. Make its documentation and implementation match those
of user_mapping_options. One might argue for stronger qualifications,
but these have long, documented tenure. pg_user_mappings has always
exhibited this problem, so back-patch to 9.2 (all supported versions).

Michael Paquier and Feike Steenbergen. Reviewed by Jeff Janes.
Reported by Andrew Wheelwright.

Security: CVE-2017-7486

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3eefc51053f250837c3115c12f8119d16881a2d7

Modified Files
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doc/src/sgml/catalogs.sgml | 7 ++--
src/backend/catalog/system_views.sql | 10 +++---
src/test/regress/expected/foreign_data.out | 54 ++++++++++++++++++++++++++++++
src/test/regress/expected/rules.out | 4 ++-
src/test/regress/sql/foreign_data.sql | 15 +++++++++
5 files changed, 82 insertions(+), 8 deletions(-)