Enhancement: return the highlighted buffer instead of outputting it

```
I'd like to use this with an SVN viewer I wrote (which uses PHPTAL to generate 
XHTML), but without the ability to return a highlighted buffer instead of 
outputting it, I'd be resorting to some bad ob_* hacks that I would rather not 
do.
```

Original issue reported on code.google.com by `lord2800@gmail.com` on 13 Dec 2010 at 8:45
