const in callbacks

[arnetheduck]

Since callback signatures are now generated in C++, might as well go ahead and retain const and the pointer type, removing a const_cast in the process.

[mappu]

Thank you - the void* was a holdover from when the dynamic_cast stuff was a bit more dodgy. It's great to have the real type parameter present there.

I was worried about the const comment about CGO compatibility, but i tried some small examples and everything works fine in my testing.

🚢

[mappu]

It looks like this only changed the cpp, not the header, so the function prototype differs from the implementation. That's probably why there were no issues with the Go side.