bit/pixel format, not planer format. Assign MSB for cursor mask and
LSB for cursor image, where 10 means mask color and 11 for image color.
Image bit order of Bt431 and Bt459 are opposite to MIPS/Alpha processors
while IMS G332 and DC503 (PCC) are indentical.
- Assume that cursor images are 32 pixel padded as ULTRIX/DU ws interface
do. It's natural to X server.
- XXX Vast majority of codes are duplicated between mfb<->tfb and cfb<->sfb.
Code sharing might be achieved in the context of TGA/SFB+ merge.
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