v3: drop negative cursor value code.
I've tested fixing the comp_clause length to 4 and didn't find any problems. Imagining the application code, I think it should be fine. Nevertheless, I can't be sure that there are no applications written in an unusual way.
The actual MS clause concept is more complex and may have comp_clause larger than 4. If we can extend the concept further in the future, I think we'll need something like get_comp_clause_count, set_comp_clause, set_comp_attr.