Only update profile fields in the database if they've actually changed.

Spotted by Stephen C on the forums:
http://mahara.org/interaction/forum/topic.php?id=1023#post4942

Signed-off-by: Nigel McNie <nigel@catalyst.net.nz>

htdocs/artefact/internal/index.php

@@ -350,12 +350,14 @@ function profileform_submit(Pieform $form, $values) {
             }
         }
         else {
+            if ($values[$element] != $profilefields[$element]) {
                 $classname = generate_artefact_class_name($element);
                 $profile = new $classname(0, array('owner' => $USER->get('id')));
                 $profile->set('title', $values[$element]);
                 $profile->commit();
             }
         }
+    }
 
     try {
         db_commit();