SL and AUTH modules merged

Finally I found the time to merge two important modules that existed in Kamailio (OpenSER) and SIP Express Router (SER):

• sl - stateless reply functions
• auth - common API for www digest authentication

Their importance is given by the usage from other modules. SL really required many other modules to be updated.

For both modules was not a simple code integration, but also addition of new features:

• sl - ability to execute event_route[sl:filtered-ack] when an ACK to a SL reply is received
• auth - refurbished pv_www_authenticate() and pv_proxy_authenticate()

For Kamailio (OpenSER) users, the new auth module brings many improvements in terms of security and performance, mainly related to one-time nonce and qop auth-int.

After this merge, several duplicated modules became easier to merge, targeting them before releasing 3.1.0. Stay tuned!