INT 10H 1017H: Read a Block of DAC Color Registers

                                                          Compatibility: VGA
 Expects: AX    1017H
          BX    first DAC register to read (0-00ffH)
          CX    number of registers to read (0-00ffH)
          ES:DX addr of a buffer to hold R,G,B values (CX*3 bytes long)
 Returns: ES:DX buffer contains returned data
    Info: This obtains the current 18-bit RGB values of a consecutive block
          of DAC color registers.

          On entry, the buffer at ES:DX must be large enough to hold the
          requested data.  Each register takes 3 bytes, so the buffer must
          be CX*3 bytes long.

          On return, the table is laid out as Red,Green,Blue,
          Red,Green,Blue, ... etc.  Only the low-order 6 bits of each byte
          has meaning.  See INT 10H 1010H for background info on 18-bit RGB
          values for DAC color registers.

   Notes: Use INT 10H 1012H to program a block of DAC registers.
          See INT 10H 1013H for a reason why you might tend to work with
          16- or 64-register blocks.

See Also: INT 10H 10H: EGA/VGA Palette Functions
          INT 10H: Video Services
          EGA/VGA Data Areas
          VGA I/O Ports