pgsql: Add some basic tests of GUC behavior.

Log Message:
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Add some basic tests of GUC behavior.
Joachim Wieland

Modified Files:
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    pgsql/src/test/regress:
        parallel_schedule (r1.32 -> r1.33)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/parallel_schedule.diff?r1=1.32&r2=1.33)
        serial_schedule (r1.30 -> r1.31)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/serial_schedule.diff?r1=1.30&r2=1.31)

Added Files:
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    pgsql/src/test/regress/expected:
        guc.out (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/guc.out?rev=1.1&content-type=text/x-cvsweb-markup)
    pgsql/src/test/regress/sql:
        guc.sql (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/guc.sql?rev=1.1&content-type=text/x-cvsweb-markup)