phpbb: Make the username case-insensitve on login again. The username field in the phpbb3 database is case sensitive (i.e., it has utf_bin collation), whereas in phpbb2 it was case insensitive. This commit changes the SQL query to make logins case insensitive again, since a lot of people used a capital letter for registering their username, but forgot that later on...
phpbb: Update to authenticate agains PhpBB version 3. This removes checks for the group_single_user column which got removed and changes the password hash. For the latter, a separate library is used, which is included in this commit.
phpbb: Properly handle case (in)sensitivity in usernames. By default, the phpbb database makes username checks case insensitive. To compensate for the fact that ACL checks are case sensitive, we thrash the username from the request after a sucessful password check (since that username might have "wrong" casing) and use the username from the database instead.
phpbb: Restructure to make PhpbbAuth and PhpbbGroupsBackend more equal. Previously, you would instantiate the PhpbbAuth class and the groups backend constructor would be a member of that. Now, there is a setup function that returns an instantiated PhpbbAuth object and a PhpbbGroupsBackend constructor.