pages: Translate Special Characters

This addresses issue #3842 where special characters in a Page name causes a
403 or 404 error. This adds a method to convert the special characters to
html entities and then removes the entity suffixes leaving only
un-accented characters behind. (e.g. 'ã' => 'ã' => 'a')

include/class.format.php

@@ -737,6 +737,13 @@ class Format {
     // Thanks, http://stackoverflow.com/a/2955878/1025836
     /* static */
     function slugify($text) {
+        // convert special characters to entities
+        $text = htmlentities($text, ENT_NOQUOTES, 'UTF-8');
+
+        // removes entity suffixes, leaving only un-accented characters
+        $text = preg_replace('~&([A-za-z])(?:acute|cedil|circ|grave|orn|ring|slash|th|tilde|uml);~', '$1', $text);
+        $text = preg_replace('~&([A-za-z]{2})(?:lig);~', '$1', $text);
+
         // replace non letter or digits by -
         $text = preg_replace('~[^\p{L}\p{N}]+~u', '-', $text);