Protocol spec missing errors for invalid primaries

Some issues we've noticed while implementing support for xx_image_description_creator_params_v2_interface, related to set_primaries() and set_mastering_display_primaries():

1. These functions do not accept negative x,y values for now. Should we change that?
2. We have no errors for absurd values (out of a valid range). Should we add that?
3. Clients may pass invalid white points outside the primaries triangle, and we have no error for that. Maybe we should use invalid_primaries and invalid_mastery for that?

As this is all related to "bad primaries", decided to keep this in a single issue.