INT 10 - EGA Register Interface Library - READ ONE REGISTER
        AH = F0h
        BL = register number
        BH = 00h
        DX = group index
            Pointer/data chips
               00h CRT Controller (25 reg) 3B4h mono modes, 3D4h color modes
               08h Sequencer (5 registers) 3C4h
               10h Graphics Controller (9 registers) 3CEh
               18h Attribute Controller (20 registers) 3C0h
            Single registers
               20h Miscellaneous Output register 3C2h
               28h Feature Control register (3BAh mono modes, 3DAh color modes)
               30h Graphics 1 Position register 3CCh
               38h Graphics 2 Position register 3CAh
Return: BL = data
Note:   the RIL is provided by EGA.SYS, the Microsoft Mouse driver, the OS/2
          compatibility box, and others
SeeAlso: AH=F2h,INT 2F/AX=BC00h