INT 31 P - DPMI 0.9+ - GET STATE SAVE/RESTORE ADDRESSES
        AX = 0305h
Return: CF clear
        AX = size in bytes of state buffer
        BX:CX = real mode address of procedure to save/restore state
        SI:DI / SI:EDI = protected mode procedure to save/restore state
Notes:  the buffer size will be zero if it is not necessary to preserve state
        16-bit programs should call SI:DI, 32-bit programs should call SI:EDI
        this function is only needed if using the raw mode switch service

Values to call state-save procedures with:
        AL = direction
            00h save state
            01h restore state
        ES:DI / ES:EDI -> state buffer
Return: all registers preserved