INT 7A - IBM 3270 Workstation Program API - Multi-DOS
        AH = 09h
        BX = 8020h
        CX = 00FFh
        ES:DI -> control block
        DX = ID of INDJQRY
                get environment size
           = ID of INDJASY
                request DOS functions from workstation
           = ID of MEMORY
                AL = function
                    01h allocate memory
                    02h deallocate memory
                    03h modify allocated size
Return: ???