pgsql: Fix plperl validator to honor check_function_bodies: when that is

Log Message:
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Fix plperl validator to honor check_function_bodies: when that is OFF,
we want it to check the argument/result data types and no more. In
particular, libperl shouldn't get initialized in this case.

Modified Files:
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pgsql/src/pl/plperl:
plperl.c (r1.96 -> r1.97)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plperl/plperl.c.diff?r1=1.96&r2=1.97)