INT 15 - DESQview v2.50+ - "GETDVXVERSION" - GET DESQview/X VERSION
        AX = DE30h
Return: BX = version (BH=major, BL=minor) or 0000h if not DESQview/X
Notes:  DESQview 2.50-2.52 are distributed as part of DESQview/X v1.0x.
        you must first check the DESQview version to verify that it is 2.50 or
          greater