In the HTML outputted from get_search_form(): increment the ID connecting <label> to <input> when the function is called multiple times, remove the form and submit button IDs for HTML 5.0 and for XHTML after the first call. Props WraithKenny, fixes #16539

git-svn-id: http://core.svn.wordpress.org/trunk@23801 1a063a9b-81f0-0310-95a4-ce76da25c4cd