NEW:      RDDSETDEFAULT() function
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     RDDSETDEFAULT() is an RDD function that sets or returns the name of the
     previous default RDD driver and, optionally, sets the current driver to
     the new RDD driver specified by <cNewDefaultRDD>.  If <cNewDefaultRDD>
     is not specified, the current default driver name is returned and
     continues to be the current default driver.

     This function replaces the DBSETDRIVER() function.