Bug#650458: rsvg-convert: Error parsing option -b

[Yuriy M. Kaminskiy]

This seems was fixed somewhere between wheezy (2.36, only checked 
sources, likely broken) and jessie (2.40.5, tested, seems fixed):
as of jessie `rsvg-convert -b white` works as expected, and there are no 
traces of base-uri options in sources anymore (by NEWS, probably in 
2.39.0, when loading resources from the net was removed?).