1. DefNode.has_fused_arguments was set too early (before
locals/annotations) were evalutated, so function was not treated
as fused.
2. When re-evaluating the specializations of the fused function
it was treated as a redefinition because the locals/annotation was
reapplied over the specialized type.
3. Including annotation as string (required changes to
StringNode.analyse_as_type), and extra tests for fused type defined
as cython.fused_type in the Py file