[Users] New features added to OpenSer - BLA support and XMPP presence gateway

Two new modules were just introduced to SVN -- both are related to presence services. 1) pua_bla - implements Bridged Line Appearances according to the specifications in draft-anil-sipping-bla-03.txt. BLA, aka Shared Call/Line Appearance, comes from old telephony, where many devices share same line. Translated to SIP, means that many SIP devices share same AoR, but only one call can be established at a time, either addressed or initiated from the line. The call can be put on hold, and the others devices are notified so that they can pick up the call (the typical example is that with the secretary answering the call and putting it on hold to be picked up by the boss). The SIP devices must have client-side support for BLA as well. In out tests we used POLYCOM SoundPoint IP 430 SIP phones. The behaviour for this specific device: when picking up the handset form one phone a red light appears at the other phones. If attempting to call from a second phone using the same line, you get the message "Resources full". If a call is established, when putting it on hold, the light starts to flicker at the other phones and it is possible to pick it up. 2) pua_xmpp - is a presence gateway between SIMPLE and XMPP. It comes to complete the IM gateway, by enabling presence state information exchange between SIP/SIMPLE and Jabber/XMPP clients. For testings we used Gaim 2.0.0beta5, Psi v0.10 for XMPP and Xlite v3.0 for SIP. Some sample config file to implement above features will be published soon on dokuwiki.