PHP 5.3 suport & Success handlers loading bugfix

- Callable typehint removed
- Success handler called via call_user_func rather than via $handler(...)
- Username is not altered to username@fqdn in the username generator, since this fucks up with the sAMAAccountName lookups in default success handlers. The default success handlers search for pre-2000 username in LDAP (maybe fix in the future to something more relaiable?)