Make display EOTFs in built-in transforms mirrored and unclamped to preserve sub-black and super-white

[nick-shaw]

In broadcast scenarios it is necessary for all processing to pass both sub-black and super-white values. BT.2111 test patterns, for example, include PLUGE, and the ramp goes from -7 to 109%. Broadcast engineers expect conversion to pass these values, so a config for broadcast use cannot currently be created using the built-in XYZ-D65 to display transforms.