Improve Cython backend for skimage
Created originally on Bitbucket by paugier (Pierre Augier)
Was already merged in Bitbucket before import, marked as merged by the import user
- Tasks skimage
- nonecheck and cdivision
- positive_indices
- Prepare new _make_header_from_fdef_annotations for Cython
- New _make_header_from_fdef_annotations for the Cython backend (more correct fused types)
- Document Cython issues with nogil and pure-Python mode
- Small changes short_repr typing
- void and doc