add simplistic IuUP FSM and strip/add IuUP headers

This should really be using the FSM in libosmocore/laforge/iu_up: take the best
of both sides and integate in the libosmocore FSM implementation, then use it
here.
- in libosmocore, the FSM definition is nicer.
- here, we have correct header checksums.

This patch here also adds RTP header stripping/adding functionality, after
introducing using msgb to pass data around.

Change-Id: Ibc70e0aa00476926dd1f4ea8139c34f31f9cdfa3
diff --git a/configure.ac b/configure.ac
index 6f6ad4b..1278816 100644
--- a/configure.ac
+++ b/configure.ac
@@ -206,6 +206,7 @@
     tests/atlocal
     tests/mgcp_client/Makefile
     tests/mgcp/Makefile
+    tests/iuup/Makefile
     doc/Makefile
     doc/examples/Makefile
     doc/manuals/Makefile