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/src/libosmo-mgcp/Makefile.am b/src/libosmo-mgcp/Makefile.am
index 587bdd4..7314b22 100644
--- a/src/libosmo-mgcp/Makefile.am
+++ b/src/libosmo-mgcp/Makefile.am
@@ -40,4 +40,6 @@
 	mgcp_conn.c \
 	mgcp_stat.c \
 	mgcp_endp.c \
+	iuup_protocol.c \
+	iuup_cn_node.c \
 	$(NULL)