QUICKFIX: Let the database perform both lowercase operations

The attached patch uses the SQL LOWER() function instead of mixing usage of LOWER() and PHP strtolower(). The latter is not UTF8 aware, but the database/connection might be configured to be UTF8 aware, so the results might not be the same for all strings. It is generally better to not use functions thought to be the same, but implemented in different environments, to check for equality.

Note that this applies to DRUPAL-4-5 as well, in fact I have seen this error in there.