many bugfixes and improvements for multicall

[linphone] / oRTP

diff --git a/oRTP b/oRTP
index a084620745b1b1c81ec93501ffbb3de373f7c8c9..d2a8cb0890c7547703a092c839c55db10449ef92 160000 (submodule)
--- a/oRTP
+++ b/oRTP
@@ -1 +1 @@
-Subproject commit a084620745b1b1c81ec93501ffbb3de373f7c8c9
+Subproject commit d2a8cb0890c7547703a092c839c55db10449ef92