Updating Drupal user may fail with fatal PHP error when related CiviCRM contact has no email addresses

I've marked this as "Major" only because a fatal PHP error is somewhat bad, but in reality I suspect that this scenario is not terribly likely, although I hit it.

Steps to reproduce:

1) Create a new Drupal user.
2) Go to the auto-created CiviCRM user and remove the email address from the contact.
3) Attempt to change the email address of the Drupal user.

You should be presented with: "Fatal error: Class 'CRM_Core_DAO_Email' not found in /var/www/zupport.creativecommons.org/www/sites/default/modules/civicrm/CRM/Core/BAO/UFMatch.php on line 375"

After speaking with Lobo on #civicrm he figures that it's fine to just add the following line right above line 375 of UFMatch.php

require_once 'CRM/Core/DAO/Email.php';

The attached patch seems to resolve the issue.