Create a wrapper.h Header

The wrapper.h file will include all the various headers containing declarations of structs and functions we would like bindings for. In the particular case of bzip2, this is pretty easy since the entire public API is contained in a single header. For a project like SpiderMonkey, where the public API is split across multiple header files and grouped by functionality, we'd want to include all those headers we want to bind to in this single wrapper.h entry point for bindgen.

Here is our wrapper.h:

#include <bzlib.h>

This is also where we would add any replacement types, if we were using some.