pgsql: Document that libpq's PQgetResult() should be called after a fat

Document that libpq's PQgetResult() should be called after a fatal error
to fully process errors.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/06711de9d9d4e122d4e4c9b801b471e048281f48

Modified Files
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doc/src/sgml/libpq.sgml | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)