plot issues -> favor pdfcairo

[John W. Eaton]

On  6-Jun-2009, Ben Abbott wrote:

| I've attached a changeset for the pdf part. It is combined with a  
| changeset for forcing mono rendering (there is some problem with  
| rgb2gray that has delayed me in pushing that change).
| 
| In any event, I'd appreciated confirmation form linux and window's  
| users that this chageset works correctly.

Have you applied this changeset?

| +	  ## FIXME - Why doesn't rgb2gray work?
| +	  ##         color = rgb2gray (color);

Core parts of Octave should not rely on rgb2gray since it is part of
the image package.

jwe