[COMMITTERS] pgsql: Require update permission for the large object written bylo_put

Require update permission for the large object written by lo_put().

lo_put() surely should require UPDATE permission, the same as lowrite(),
but it failed to check for that, as reported by Chapman Flack.  Oversight
in commit c50b7c09d; backpatch to 9.4 where that was introduced.

Tom Lane and Michael Paquier

Security: CVE-2017-7548

Branch
------
REL9_5_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/873741c6821d4fe8245b97e2adf1e8142c8b7531

Modified Files
--------------
src/backend/libpq/be-fsstubs.c           | 12 ++++++++++++
src/test/regress/expected/privileges.out | 10 ++++++++++
src/test/regress/sql/privileges.sql      |  4 ++++
3 files changed, 26 insertions(+)