Update TODO.md
Implement ICallable#instance_ownership_transfer

This method was not available before version 1.42 of
gobject-introspection, so a version check is included.
Increase refcount for receiver arguments with full ownership transfer
Add a TODO
Update test to show need for increasing refcount
Extract method BaseArgumentInfo#ownership_transfer
Update changelog
Improve reference handling [merges 'fix-refs']
Avoid errors when coveralls is not present in CI