python
[mypyc] Support inheriting native int attributes from traits
Regular trait attributes are accessed via looking up the field offset from a vtable. This doesn't work with native ints, since they may also require access to a defined attributes bitmap, and also looking that up from a vtable would be too complicated.
Work around this may always accessing trait native int attributes using accessor methods. These can raise an exception if an attribute is undefined.
Add empty accessor methods in traits for each attribute with overlapping error values. Also synthesize real accessors in each concrete subclass.
When accessing the attribute using a concrete subclass, still prefer direct field and bitmap access. Only attribute access through a trait type requires accessors to be used.
Work on mypyc/mypyc#837.
