Wrap characters are not used when the --markup option is choosing

To reproduce:

```
python pangosyntaxhighlight.py py pangosyntaxhighlight.py out.mu
paps --show-wrap --wrap=char -o out.pdf --markup out.mu
```

where `pangosyntaxhighlight.py` comes from: https://github.com/thiemol/pango-syntax-highlighter