Figure out why AST nodes can't be freed

[incrediblesound]

For some reason freeing an AST node causes a segfault. This may be because they reference other pointers that need to be freed or because there is corruption happening somewhere.

[TheLoneWolfling]

The content of AST nodes are referenced all over the place.

We'd need to do defensive copies of AST node content in order to be able to free them.