Clamp opacity value to range 0 to 1
Clamp opacity value to range 0 to 1

Our opacity parsing function allows
* number values outside range 0.0 to 1.0
* %-values.

However this is incorrect behavior.
* http://www.w3.org/TR/SVG11/painting.html#FillOpacityProperty
* http://www.w3.org/TR/SVGTiny12/painting.html#FillOpacityProperty

GNOME/librsvg,GNOME/librsvg,GNOME/librsvg,GNOME/librsvg