* ast/rust-ast.h: Change Path API to be more consistent.
* ast/rust-path.h: Likewise.
* ast/rust-ast-collector.cc (TokenCollector::visit): Use new API.
* resolve/rust-ast-resolve-item.cc (ResolveItem::visit): Likewise.
* resolve/rust-ast-resolve-path.cc (ResolvePath::resolve_path): Likewise.
* resolve/rust-forever-stack.hxx: Likewise.