drupal_set_title needs to be run through PASS_THROUGH in order to not double encode the title

Example HTML title and H1 produced by the diff module on pages like /node/190/revisions

<title>Revisions for Charlie&amp;#039;s Test Project1 | Example.com</title>
<h1 class="title" id="page-title">Revisions for Charlie&amp;#039;s Test Project1</h1>

Note the double encoding. Diff should follow core, for node.pages.inc line 501:

drupal_set_title(t('Revisions for %title', array('%title' => $node->title)), PASS_THROUGH);

I propose a patch so diff does the same, on diff.pages.inc line 23:

drupal_set_title(t('Revisions for %title', array('%title' => $node->title)), PASS_THROUGH);

Fixes all our issues quite nicely, can role a patch if you really want, but this is a one liner that has already been extensively tested (it is in core currently)