unit accessors

In doing ACTION-3414, I've added unit accessors to SVGAnimatedLength, so 
that you can now do:

   rectElement.x.px = 20;

I've also added these to SVGAnimatedLengthList, where they reflect the 
first SVGLength in the base value list.  This is so that

   textElement.x.px = 20;

will also work.

One issue: should we have one for percentages, and if so, what should it 
be named?

Received on Wednesday, 6 February 2013 05:50:48 UTC