#342 ddjvu subsample output does not match expected input of djvumake

[Robert Mast]

With a picture of 2480x3500 when I ask ddjvu to subsample the foreground and background-images by 6 or 3 both give "djvumake: FG44 subsampling is not in [1..12] range"

djvumake expects a foreground picture of 414 pixels wide, while ddjvu's output is 413 pixels wide.
Same story with slightly different numbers for the background-picture.