pgsql: Back-patch non-static ExecuteSqlQueryForSingleRow().

Back-patch non-static ExecuteSqlQueryForSingleRow().

Back-patch a subset of commit 47e59697679a0877e0525c565b1be437487604a7
to 9.4 and 9.3.  The next commit adds calls to this function.

Security: CVE-2018-1058

Branch
------
REL9_4_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/461c32b557ddbb0ed67b4b2232a191554ad40c3c

Modified Files
--------------
src/bin/pg_dump/pg_backup_db.c | 23 +++++++++++++++++++++++
src/bin/pg_dump/pg_backup_db.h |  1 +
src/bin/pg_dump/pg_dump.c      | 24 ------------------------
3 files changed, 24 insertions(+), 24 deletions(-)