[css3-mediaqueries] should be clear whether spaces allowed around /

In http://dev.w3.org/csswg/css3-mediaqueries/#aspect-ratio (and
device-aspect-ratio) it is not clear whether spaces are allowed
around the '/'.  It should be clear.

I also think they should be allowed.

-David

-- 
L. David Baron                                 http://dbaron.org/
Mozilla Corporation                       http://www.mozilla.com/