OGRStyleTool::GetRGBFromString defaults alpha to 0.

[dev@…]

The function OGRStyleTool::GetRGBFromString defaults the alpha value to
zero and there is no way when using this function to know if the returned
value is the default value or the value specified in the color string. 
The default value should normally be set to 0xFF as specified in the doc.

[warmerdam]

Review and fix before GDAL 1.2.0 release.

[warmerdam]

Frédéric,

I'm very sorry it took so long to fix this problem.  It certainly wasn't hard
to correct. I have committed a fix to default alpha to 255 (0xff) if there
is no alpha in the RGB string. 

I haven't actually tested it, other than to build it.