[Xastir] Update Notice: OSM tile support changes

[Tom Hayward]

>
> Try selecting the three new topOSM maps. Set the relief to level 0,
> contours to level 1 and features to level 2. Note that the tiles are
> only available for the west coast of the US. See http://toposm.com/.
> My implementation in Xastir doesn't look as good as the web based
> because of alpha blending issues.
>

The transparency doesn't seem to work on Mac OS X (with GraphicsMagick). I'm
seeing just the top layer with gray background (with my Xastir background
configured to White). Let me know if you need a better description.

Anyone else seeing this? I could have missed a step in the install process
(I just rebuilt GraphicsMagick with fink to get JPEG working).


Tom KD7LXL