INT 67 - EEMS - PAGE MAPPING
        AH = 6Ah
        AL = subfunction
            00h save partial page map
                CH = first page frame
                CL = number of frames
                ES:DI -> buffer which is to be filled
            01h restore partial page map
                CH = first page frame
                CL = number of frames
                DI:SI -> previously saved page map
            02h save and restore partial page map
                CH = first page frame
                CL = number of frames
                ES:DI = buffer for current page map
                DI:SI = new page map
            03h get size of save array
                CH = first page frame
                CL = number of frames
                Return: AL = size of array in bytes
            04h switch to standard map register setting
            05h switch to alternate map register setting
            06h deallocate pages mapped to frames in conventional memory
                CH = first page frame
                CL = number of frames
Return: AH = status
Note:   similar to EMS function 4Eh, except that a subrange of pages can be
          specified