pgsql: Change warning-silencing code not to cast the pointer type,

Log Message:
-----------
Change warning-silencing code not to cast the pointer type, instead
casting the value of the variable later.

Per comments from Tom.

Modified Files:
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pgsql/src/test/regress:
pg_regress.c (r1.58 -> r1.59)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/pg_regress.c?r1=1.58&r2=1.59)