MDL-62680 output: Only hide icons with no label

For accessibility we don't want to read an icon with a label immediately next to the label,
but in this case it's clearer for the icon to have no alt text / title for both
screen readers and non-screen readers. Worse is not reading important information just
because it's displayed as an icon.

lib/classes/output/icon_system_fontawesome.php

@@ -444,6 +444,9 @@ class icon_system_fontawesome extends icon_system_font {
         if (!$subpix->is_mapped()) {
             $data['unmappedIcon'] = $icon->export_for_template($output);
         }
+        if (isset($icon->attributes['aria-hidden'])) {
+            $data['aria-hidden'] = $icon->attributes['aria-hidden'];
+        }
         return $output->render_from_template('core/pix_icon_fontawesome', $data);
     }