- bring CSS lexer to the CSS2.1 spec (http://www.w3.org/TR/CSS2/syndata.html)
- CSS override rules are broken. For example, text-offset-y and text-offset
  should override each other, but currently they are mixed upon rendering.
  Does it matter?
- Fixing of label positions should include some margin
- Clean up shp.c

- Add icon-anchor-* properties like text-anchor-*
  (for now, we have only icon-offset-*)

- do something with (major-)z-index-fixup ... better typesetting of bridges?
- way[layer="2"] requires quotes