pgsql: Hot-fix ecpg regression test for missing ecpg_config.hinclusion

Hot-fix ecpg regression test for missing ecpg_config.h inclusion.

I don't think this is really the best long-term answer, and in
particular it doesn't fix the pre-existing hazard in sqltypes.h.
But for the moment let's just try to make the buildfarm green again.

Discussion: https://postgr.es/m/151935568942.1461.14623890240535309745@wrigleys.postgresql.org

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/4ca492425cd99efc6827c265d4d5a60f65971ae9

Modified Files
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src/interfaces/ecpg/test/expected/sql-sqlda.c | 4 ++--
src/interfaces/ecpg/test/sql/sqlda.pgc        | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)