1.0.11:  Allow overriding "style" attribute (via IAL) in lists and spans
As in:

```markdown
{:req: counter="bar" style="format R(%d)"}

{: req}
* Foo
* Bar
* Bax

Fasel.

* Foof
* Barf
* Barx
{: req}
```

Also: clean up some backward compatibility for old kramdown versions.