Rounds the range implied by the virtual addresses in a retadr
    array returned from a memory management system service to a range
    that is the factor of CPU-specific pages. The return value can be
    supplied as an inadr array in a subsequent call to another memory
    management system service.

    Format

      $ROUND_RETADR  retadr, full_range, user_mask_addr,

                     direction=ASCENDING