Prevent user from trying to move a page to a title longer than 255 bytes.

Prevent user from trying to move a page to a title longer than 255 bytes.

This just puts a maxlength on the field (+ byte counter js) which is much
nicer and clearer feedback to the user if they went over the limit then:
"The requested page title was invalid, empty, or an incorrectly linked inter-language or inter-wiki title. It may contain one or more characters which cannot be used in titles"
Which doesn't exactly indicate a length error.