Add a default filter to `title_save_pre`: `trim`, because extra whitespace.

Props nikolov.tmw, avryl.
Fixes #19904.

Built from https://develop.svn.wordpress.org/trunk@29801


git-svn-id: http://core.svn.wordpress.org/trunk@29568 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/default-filters.php

@@ -191,6 +191,7 @@ add_filter( 'editable_slug',            'esc_textarea'                        );
 add_filter( 'nav_menu_meta_box_object', '_wp_nav_menu_meta_box_object'        );
 add_filter( 'pingback_ping_source_uri', 'pingback_ping_source_uri'            );
 add_filter( 'xmlrpc_pingback_error',    'xmlrpc_pingback_error'               );
+add_filter( 'title_save_pre',           'trim'                                );
 
 add_filter( 'http_request_host_is_external', 'allowed_http_request_hosts', 10, 2 );