Otherwise it may be confusing, as in "does format_stream() write to
that path?".

All work is done through writer.class_writer().append()

They are now defined within the connect_func, instead in separate functions.

One of the examples is for a derived GTK widget, and all the tests use
gobject_class to import the proc macro's requirements.

All the changed lines use values which are a TokenStream, not a
Vec<&dyn ToTokens>.