Fix JS truncate of test that contains new lines characters

Default maxlength truncate algorithm has week place - even after truncating string can be longer than limit.
This is because javascript substr functions count new lines as one character not two as it have to be.

Example:
After we run obj.val().substr(0, 100) and then calculate string length with count = ml.twochar_lineending(obj.val()).length we could get count to be more that 100 (depends on how many new lines characters are found).

To fix this issue i have created patch - that will apply string truncation untill string will be no longer than limit taking into account new lines characters.

Note - i have created patch only for case when maxlength applied on simple textarea field, not WYSIWYG.