pgsql: Return proper exit code (3) from psql when ON_ERROR_STOP=on and

Log Message:
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Return proper exit code (3) from psql when ON_ERROR_STOP=on and
--single-transaction are both used and the failure happens in commit,
e.g. failed deferred trigger. Also properly free BEGIN/COMMIT result
structures from --single-transaction.

Per report from Dominic Bevacqua

Tags:
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REL8_4_STABLE

Modified Files:
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pgsql/src/bin/psql:
command.c (r1.206 -> r1.206.2.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/command.c?r1=1.206&r2=1.206.2.1)