Add support for reversible JP2K DICOM (trivial patch)

[jcupitt]

Lossless JP2K usually has PhotometricInterpretation set to YBR_RCT (reversible YCbCr). OpenJPEG does the conversion to RGB, so we can just use the RGB path in this case.

See https://github.com/openslide/openslide/issues/662

[openslide-bot]

DCO signed off :heavy_check_mark:

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[jcupitt]

The linked issue has a couple of sample images which load correctly with this PR.

[dclunie]

What is the status of this?

[dclunie]

@bgilbert I guess this didn't make it into the latest release (4.0.0.10) :(

[bgilbert]

4.0.0.10 is just the tenth binary build of 4.0.0, with updated dependencies etc.. The OpenSlide code is the same.

This is still on my radar. The plan is to finish some infrastructure changes so we can more easily add new test slides within the limitations of the GitHub CI runners.