Generate Typescript Type Definition File (.d.ts) from clang AST.

I found a method of obtaining clang AST from emcc/em++.

```
emcc -Xclang -ast-dump -fsyntax-only -fno-color-diagnostics "${asbPath}.c"
```

I interest myself in the following AST nodes:

- FunctionDecl
- LinkageSpecDecl
- TypedefDecl
- TypeAliasDecl

Maybe, they will tell about (extern "C") function name and its arguments type...