pgsql: Add missing --use-existing --help mention from regression binary.

Log Message:
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Add missing --use-existing --help mention from regression binary.

Jan Urba?ski

Modified Files:
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pgsql/src/test/regress:
pg_regress.c (r1.71 -> r1.72)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/pg_regress.c?r1=1.71&r2=1.72)