INT 67H 4200H: Get EMS Memory Total / Available

                                                     Compatibility: EMS 3.2+ 
 Expects: AX    4200H
          ──────────────────────────────────────────────────────────────────
 Returns: AH    EMM status (0=successful)
          DX    total pages (16K units)
          BX    available pages (16K units)
          ──────────────────────────────────────────────────────────────────
    Info: Obtains the total amount of EMS memory that is supported and the
          amount that is currently available.

   Notes: DOS 6.0+ EMM386 draws EMS from the same pools as XMS▲; so the
          returned values may vary from time to time.

See Also: INT 67H: EMM Services
          Extended Memory Specification (XMS)
          Interrupts and BIOS Services
                                    -♦-