update ms2 and cleanup dead function

[linphone] / mediastreamer2

diff --git a/mediastreamer2 b/mediastreamer2
index 2720ab1d1568ced6f0bf63e454a35f340d8ace64..23b802c4631fdf909a218a0dd0a77c6cf6d4d5a9 160000 (submodule)
--- a/mediastreamer2
+++ b/mediastreamer2
@@ -1 +1 @@
-Subproject commit 2720ab1d1568ced6f0bf63e454a35f340d8ace64
+Subproject commit 23b802c4631fdf909a218a0dd0a77c6cf6d4d5a9