Redmine

I’ve attached a patch that extends CommonMark list autocompletion.
It also refactors the code by splitting functions and using named capture groups.

Examples:

- [ ] uncheck task↵
- [ ]

- [x] checked task↵
- [ ]

1) [ ] ordered task↵
2) [ ] 

Setting the target version to 6.1.1.

Committed the fix in r24057. Thank you.

Merged the fix into 6.1-stable branch in r24064.