Relative URLs are not absolutified in unparseable CSS

```
We can parse CSS2.1 but not CSS3.x.
We rewrite what we can parse and leave the unparseable CSS unchanged.
This can be a problem if there are URLs in the unparseable CSS because they 
won't be absolutified, which is sometimes required.

This is fixed in release 0.10.22.x
```

Original issue reported on code.google.com by `matterb...@google.com` on 23 May 2012 at 1:06
