- pix-rotate-shearprocedure
- in - PPIX
- in - XCENT YCENT - x, y center of rotation
- in - ANGLE - radians, + is clockwise
- in - INCOLOR - fill-in from edges: select IN-WHITE or IN-BLACK
- (pix-rotate-shear ...) isn't recommended for angles >20deg (.35rad)
- returns: rotated ppix, or #f if error.