greying out cells in a sequence dialog item

[Ranson <ranson@LANNION.cnet.fr>]

If you want to draw in "real" grey, set the fore color to grey. If you want
the patterned grey (alternating black and white pixels), draw in black and
then draw the grey pattern (e.g. draw a filled rectangle) using the patBic
mode. This mode leaves the whites pixels white, and change the black pixels
to the pattern.
     Daniel.