Revert to earlier semantics so that svg and ps output have no background by default.
Revert to earlier semantics so that svg and ps output have no background by
default.

jho1965us/graphviz,BMJHayward/graphviz,ellson/graphviz,tkelman/graphviz,MjAbuz/graphviz,ellson/graphviz,pixelglow/graphviz,jho1965us/graphviz,pixelglow/graphviz,ellson/graphviz,MjAbuz/graphviz,pixelglow/graphviz,jho1965us/graphviz,tkelman/graphviz,kbrock/graphviz,tkelman/graphviz,pixelglow/graphviz,ellson/graphviz,ellson/graphviz,tkelman/graphviz,tkelman/graphviz,MjAbuz/graphviz,MjAbuz/graphviz,pixelglow/graphviz,BMJHayward/graphviz,tkelman/graphviz,pixelglow/graphviz,ellson/graphviz,MjAbuz/graphviz,jho1965us/graphviz,jho1965us/graphviz,jho1965us/graphviz,tkelman/graphviz,kbrock/graphviz,BMJHayward/graphviz,BMJHayward/graphviz,MjAbuz/graphviz,ellson/graphviz,tkelman/graphviz,kbrock/graphviz,BMJHayward/graphviz,BMJHayward/graphviz,pixelglow/graphviz,MjAbuz/graphviz,BMJHayward/graphviz,jho1965us/graphviz,kbrock/graphviz,tkelman/graphviz,kbrock/graphviz,pixelglow/graphviz,kbrock/graphviz,pixelglow/graphviz,kbrock/graphviz,BMJHayward/graphviz,kbrock/graphviz,MjAbuz/graphviz,tkelman/graphviz,jho1965us/graphviz,MjAbuz/graphviz,ellson/graphviz,MjAbuz/graphviz,ellson/graphviz,jho1965us/graphviz,pixelglow/graphviz,ellson/graphviz,tkelman/graphviz,kbrock/graphviz,kbrock/graphviz,ellson/graphviz,jho1965us/graphviz,pixelglow/graphviz,BMJHayward/graphviz,BMJHayward/graphviz,jho1965us/graphviz,kbrock/graphviz,BMJHayward/graphviz,MjAbuz/graphviz