pgsql: Fix broken extract_actual_join_clauses call in 9.6 postgres_fdw.

Fix broken extract_actual_join_clauses call in 9.6 postgres_fdw.

In commits e5d83995e et al, I changed the signature of
extract_actual_join_clauses, thinking that it was not called from
anywhere but createplan.c. I missed that postgres_fdw uses it
in the 9.6 branch only.

This opens up the question of whether any third-party modules might
be calling it, and whether we need to take steps to avoid an API break
for them. But for the moment, just get the buildfarm green again.

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/306d6e59f7511fef3e05457b15ecad0fc00b5e1e

Modified Files
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contrib/postgres_fdw/postgres_fdw.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)