sip_session2: print RTP endpoints

darcs-hash:20090430085347-b2873-855cf4bf46900a7ca2f8e6946139703c3e1242b4
sip_session2: minor change of duration formatting code

- the old version could say "0 seconds" when it was clearly more

darcs-hash:20090430092235-b2873-9410ca28955b118361731e1bea87c25ea9776f72