Support for visibility property

Inkscape hides components using "display: none",
however other SVG producers (notably Apache FOP)
sometimes use "visibility: hidden". The differences in
the context of Inkscape are trivial, but in the case of
FOP, which uses a hidden rectangle the size of the page
as a link to the next page, the differences are
significant enough.

If you can, peruse the output of FOP for a multi-page
document and you will observe that all pages aside from
the right half of the last page are all blue, obscuring
the content.

I can give you an example if you really need, but this
should be enough to give you an idea:

<g id="Page-1" style="font-family:sanserif;font-size:12"
   transform="translate(0,0.0)">
    <rect width="612.0" x="0.0" height="792.0" y="0.0"
          style="fill:none;stroke:black"/>
    <text x="72.0" y="80.0"
style="font-family:serif;font-size:10.0">
        some text here and so on...
    </text>
<!-- more text -->
<a xlink:href="#svgView(viewBox(0, 0.0, 612, 792))"
xlink:type="simple"
   xlink:actuate="onRequest" xlink:show="replace"
   xmlns:xlink="http://www.w3.org/1999/xlink">
    <rect width="306.0" x="0.0" height="792.0" y="0.0"
          style="fill:blue;visibility:hidden"/>
</a>
</g>