Add configuration directive to allow appending realm to username using LDAP

[smoku]

In my environment users authenticate to jabber using their email accounts. Their accounts are also stored in LDAP using the full address in the mail attribute. Because of this I needed to be able to append the realm to the username so it could be matched correctly. This patch adds the configuration directive <append-realm/> in c2s.xml and will append the realm to the username when preparing the search filter for LDAP users. This patch has been tested to work on SuSE 9.3 with Jabberd 2.0s9 but is so trivial it should work almost anywhere.

[smoku]

Patch by Andrew Klang <andrew.klang@…>

[smoku]

(In [165]) Integrated LDAP append-realm patch by Andrew Klang. Closes #60