Support top-level classes and free functions in AST walker.
Support top-level classes and free functions in AST walker.

While libjass will never have these, they can occur because of what's actually a compile error. Thus while the AST walker will succeed, the subsequent call to compiler.compile() will fail.

joshuabrown-ellation/libjass,Dador/libjass,joshuabrown-ellation/libjass,Arnavion/libjass,Arnavion/libjass,Arnavion/libjass,Dador/libjass,joshuabrown-ellation/libjass,Dador/libjass