It appears much more convenient to access oreg in particular via an "index
variable". To avoid repeated boilerplate, add the accessor here as a c++
operator overload. This makes smpc.h c++-only. With defines guarding the
overload, it could be reduced to C again, though I decided I don't want to
bother with testing that.
- add code loading for m68k
- incomplete scsp experiments
- the register definitions should be fairly complete,
though I did not produce actual sound yet
- fix type.h definitions
- incomplete cdblock register definitions
