Legend fails when size or color properties use attribute binding

[aboudreault]

Using a simple class:

CLASS
NAME "sdsds"
     STYLE
        COLOR 255 0 0
        SIZE [length]
        SYMBOL "circle"
     END
END

The legend is badly drawn with a size of 1... which is inapropriate for most of cases since it is just too small. If the size of a style uses an attibute binding, it would be better to determine a default size for the symbol. ie. 75% of the widht/height of the legend KEYSIZE.

For the COLOR attribute binding... we have just nothing drawn since the color is set to -1 -1 -1. We could just set the color to black if the color is using an attribute binding.

Steve, what do you think?