Expand character limit for Wrappers' fields

This issue is separated from here: #741528: How do I modify html-code generated by module?

For now, every single-line field at Superfish block configuration page has a limitation of 128 characters (maxlength="128"). But for Wrappers' fields it can be not enough. For example, if you need to add 5 or more spans or if their classes have long names.
I think, it would be better if we won't have this limit at all or at least it will be extended at several times.