Implement C/C++ bindings

[bnjbvr]

I know of at least one possible user who would like to embed this project in a C program. I've seen in the project's goals that there was an intent to implement the proposed C integration API, so filing an issue to not forget about this.

[yurydelendik]

I have some wasm2obj fixes (for my pet project) at #46, though it might provide a workaround for this issue.

[gkorland]

Is there a plan to add such binding?

[alexcrichton]

Oh this issue is actually slightly out of date! The proposed C API is implemented by the wasmtime crate where building that will generate a dynamic library named wasmtime you can link in, so this is done!