Should CGColorSpaceRef be a part of core-graphics-types?

[kvark]

I wonder if there is a guideline on what goes into the types crate and what doesn't.
In gfx-rs/metal-rs#221, we use CGColorSpaceRef as opaque type, and it would be nice to avoid depending on the whole core-graphics crate there.

[jrmuizel]

I'd say a decent guideline is that if the type is used by other non-CoreGraphics APIs opaquely it's a good candidate for core-graphics-types.

[jrmuizel]

Though I guess separating out the CGColorSpace type from the wrapper is a bit of a pain.

[jrmuizel]

That being said, I have no objection to the whole thing being moved over if it makes life easier.