Switch to sanitize_title_for_query() for Query sanitization (allows for...

Switch to sanitize_title_for_query() for Query sanitization (allows for pre-3.3 page slugs to be viewable), Don't update page slugs to new slug-types when the slug is not being changed, Don't issue a XHR if the page slug hasn't changed. Group effort props xknown, markjaquith, nacin. See #19292

git-svn-id: https://core.svn.wordpress.org/trunk@19444 1a063a9b-81f0-0310-95a4-ce76da25c4cd