initialization discards qualifiers from pointer target type

A const may be needed, the following produces the error:

PixelPacket *p = AcquireImagePixels(image,0,y,image->columns,1,&image->exception);


while this fixes it:

const PixelPacket *p = AcquireImagePixels(image,0,y,image->columns,1,&image->exception);


In other news hopefully soon I'll have an ARToolkit app for reading in jpegs using ImageMagick, and also that app will have some other more exciting attributes.