Please support the current pjsip version

Issue generated from Tuleap's migration script. Originally submitted by: Yuri (yurivict)

Build with the current pjsip-2.6 fails with missing pjsip_dlg_create_uas which is deprecated. You require pjsip-2.4. But this poses a problem for packaging systems because this requires the custom build and installation of older versions.

ring-daemon-2.2.0