Support IPTPQc2 Color Space?

This is the color space used in Dolby Vision Profile 5, adding support might help conversion between Dolby Vision Profile 5 to other common color spaces such as YUV.

The transformation matrix is documented here, https://en.wikipedia.org/wiki/ICtCp#IPTPQc2, so implementation should be easy (this is probably similar to existing ICtCp_PQ and ICtCp_HLG).