LLVM-Backend Generated Interpreter C API Documentation

The LLVM backend, in conjunction with the tool llvm-kompile, can generate object files which contain the entire definition of an K semantics as machine object code.

These object files can then be used to link the LLVM-generated interpreters into custom C code, or any language that supports C FFIs.

However, currently, the interface that the LLVM-backend generated interpreters expose is a mixture of hard-coded and compile-time generated symbols, and there is no documentation of which sybmols are exported or best practices around, e.g., which symbols are considered part of a stable API and which symbols are considered internal and should not be explicitly linked against.

Such documentation would not only enable K developers to more easily productize K by adapting to specific client needs, it would also enable more possible uses of K in the broader community.

For those reasons, I think it is worth documenting these symbols (even if the documentation is marked experimental, as needed).

Start with the LLVM backend and the llvm-kompile-generated interpreters described in the issue. Inventory the hard-coded and compile-time-generated symbols exposed by the object files, then document which are stable or internal and the recommended C FFI linking practices.