INT 2F - DESQview v2.26+ External Device Interface - DV TERMINATION
        AX = DE03h
        BX = mapping context of DESQview
        DX = handle of DESQview system task
Notes:  driver should pass this call to previous handler before doing its work
        DESQview makes this call when it is exiting, but before unhooking any
          interrupt vectors
SeeAlso: AX=DE0Fh,INT 15/AX=5407h