Compatibility: Win 3.x
Expects: AX    4002H
Returns: none
Info: VM-aware applications can intercept this fn.  The VDD calls it
when it is switching the application into the foreground.

Applications which access video memory while in the background
will be frozen by the VDD (if the screen is in an unsupported
video modes INT 2fH 4000H).  This fn notifies the VM-aware
application that it now has access to video memory.

If the application has not called INT 2fH 4000H (enable VM-
assisted video save/restore) then the VDD automatically restores
the screen before calling this fn.

- -

INT 2fH 4002H: Notify Foreground Switch