update ms2 for IOS5

diff --git a/mediastreamer2 b/mediastreamer2
index 3fab7e1b190a4d2bb4a8d7514acfa5b0bcdb4e3e..a12854a1f99d56e08a78981fc3eec0181a5c1c0d 160000 (submodule)
--- a/mediastreamer2
+++ b/mediastreamer2
@@ -1 +1 @@
-Subproject commit 3fab7e1b190a4d2bb4a8d7514acfa5b0bcdb4e3e
+Subproject commit a12854a1f99d56e08a78981fc3eec0181a5c1c0d