Create C bindings for Wasmi

[Robbepop]

Currently Wasmi has no C bindings even though the Wasm spec defines a C interface which could be implemented by Wasmi.

The huge advantage is that this would open the door for collaboration and usage of the huge C ecosystem and allow C devs to more easily use Wasmi. On top of that: C bindings would not just open doors to the C ecosystem but to most serious language ecosystems since C is the langua franka for most (if not all) serious language ecosystems.

Python bindings, C++ bindings, Java bindings all could easily follow once C bindings are established.

This issue tracks progress of implementation of C bindings for Wasmi.