Node: add a "transform" field; we'll keep it here
Node: add a "transform" field; we'll keep it here

The "transform" is not a style property, it is an attribute for each
element.  So, we'll keep it in the Node, without any extra
transformations - unlike State, which keeps a composed affine of all
the ancestor elements.

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