pgsql: Have boolean pset values checked against typical boolean values,

Log Message:
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Have boolean pset values checked against typical boolean values, rather
than only 'off'.

Modified Files:
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pgsql/src/bin/psql:
variables.c (r1.28 -> r1.29)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/variables.c?r1=1.28&r2=1.29)