MDL-50295 output: prevent 'emoji' arrows

We need to append U+FE0E VARIATION SELECTOR-15 to the arrow to ensure
our l/rarrows are displayed as text icons, not 'emoji' icons.

See http://unicode.org/reports/tr51/#Diversity for more details of why
this changed in iOS 8.3+.

lib/outputlib.php

@@ -567,8 +567,8 @@ class theme_config {
                 || false !== strpos($uagent, 'Mac')) {
                 // Looks good in Win XP/Mac/Opera 8/9, Mac/Firefox 2, Camino, Safari.
                 // Not broken in Mac/IE 5, Mac/Netscape 7 (?).
-                $this->rarrow = '▶';
-                $this->larrow = '◀';
+                $this->rarrow = '▶︎';
+                $this->larrow = '◀︎';
             }
             elseif ((false !== strpos($uagent, 'Konqueror'))
                 || (false !== strpos($uagent, 'Android')))  {