Int 2F Fn 4000  - Windows 3.x (os/2 2.x???) - Get Virtual Device Driver (  [W]

   AX = 4000h

Return: AL = 01h does not virtualize video access
        02h virtualizes the video when in text mode
        03h virtualizes the video when in text mode or single plane
        graphics modes
        04h virtualizes the video when in text mode, single plane
        graphics modes, and VGA multiplane modes
        FFh virtualizes the video fully

Note:  this function is used by display drivers to find out what capabilities
     exist for the VDD driver and also trigger the VDD driver to call
     functions 4005h and 4006h.  This function also gives the Video Driver
     hardware access to the video registers.