[css-lists-3] Clarify parsing of `list-style: inside outside`

[fantasai]

Filed by @upsuper in https://lists.w3.org/Archives/Public/www-style/2014Mar/0582.html and also related to the thread around https://lists.w3.org/Archives/Public/www-style/2014Apr/0014.html ... we have rules on what to do withnone, but not counter-styles named after list-style-position values.

[upsuper]

I think it has been fixed by moving <list-style-type> to the end of list-style value syntax, but probably not mentioned explicitly.