INT 31H 0900H: Query and Disable Virtual Interrupt State

                                                    Compatibility: DPMI 0.9+ 
 Expects: AX    0900H
 Returns: CF    NC (clear; always successful)
          AL    previous setting: 00H = virtual interrupts were disabled
                                  01H = virtual interrupts were enabled
    Info: Disables the virtual interrupt flag and returns the previous
          state of that flag.

          AH is not modified by the call, so you can return to the previous
          state immediately by calling INT 31H.

          If you don't need to know the previous state, you may simply use
          the CLI opcode.

See Also: DPMI API
          INT 2fH: Multiplex Interrupt
          DOS Functions