Rewrite of _maxlength_format_element

I would rewrite _maxlength_format_element to remove drupal_add_js settings.

I think the bevahior of maxlength should be attached to the formelement directly.
This would have quite some advantages:

much less arguments in this function
easier to handle for other forms, comments...contact etc.

new paramater: $js = TRUE

But:
_maxlength_get_values should be remove and be there as parameter

Perhaps put the validate stuff in another validate function, perhaps could be possible to use form_set_error, not sure.

Any opinions.