Fix bug in psql.

per report from sugita@sra.co.jp on Thu, 09 May 2002 11:57:51 +0900
(JST) at pgsql-patches list.

Illegal long options to pg_dump makes core on some systems, since it
lacks the last null sentinel of struct option array.

Attached is a patch made by Mr. Ishida Akio <iakio@pjam.jpweb.net>.