AAC-ELD : set an initial max ptime at 50ms

- to avoid ptime automatic growing too high when packets are losts
- setting overridden up to 100 by initial set ptime

diff --git a/mediastreamer2 b/mediastreamer2
index 6e4adda46186fdb197a6bca1dd7097b313fff09d..58745e5866d325c07255bf34225c8b621e87870b 160000 (submodule)
--- a/mediastreamer2
+++ b/mediastreamer2
@@ -1 +1 @@
-Subproject commit 6e4adda46186fdb197a6bca1dd7097b313fff09d
+Subproject commit 58745e5866d325c07255bf34225c8b621e87870b