Work in progress.  Colorspace handles most format conversion using
3-stage getline/matrix/putline process using an AYUV or ARGB
intermediate, with most functions handled by Orc.  There is also
a table of single-pass conversions, all handled by Orc.  The plan
is to add optional stages for various chroma upsampling/downsampling
algorithms, dithering, and float/int16 intermediates, and then have
Orc create multi-stage functions at runtime.