get rid of mgcp_internal.h

The file mgcp_internal.h still contains mostly definitions and types
that are relevant for mgcp_network.c and mgcp_protocol.c. Lets give
the network and protocol module its own header files, also move stuff
that does not relate to protocol and network to the appropiate places.

Change-Id: I837eaad771ed7252304db4a81c37953b70766fff
diff --git a/src/libosmo-mgcp/mgcp_msg.c b/src/libosmo-mgcp/mgcp_msg.c
index 019466e..2023a68 100644
--- a/src/libosmo-mgcp/mgcp_msg.c
+++ b/src/libosmo-mgcp/mgcp_msg.c
@@ -24,7 +24,9 @@
 
 #include <limits.h>
 
-#include <osmocom/mgcp/mgcp_internal.h>
+#include <osmocom/mgcp/mgcp.h>
+#include <osmocom/mgcp/osmux.h>
+#include <osmocom/mgcp/mgcp_protocol.h>
 #include <osmocom/mgcp/mgcp_common.h>
 #include <osmocom/mgcp/mgcp_msg.h>
 #include <osmocom/mgcp/mgcp_conn.h>