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_protocol.c b/src/libosmo-mgcp/mgcp_protocol.c
index 2a6581e..6a533c3 100644
--- a/src/libosmo-mgcp/mgcp_protocol.c
+++ b/src/libosmo-mgcp/mgcp_protocol.c
@@ -35,7 +35,9 @@
 
 #include <osmocom/mgcp/mgcp.h>
 #include <osmocom/mgcp/mgcp_common.h>
-#include <osmocom/mgcp/mgcp_internal.h>
+#include <osmocom/mgcp/osmux.h>
+#include <osmocom/mgcp/mgcp_network.h>
+#include <osmocom/mgcp/mgcp_protocol.h>
 #include <osmocom/mgcp/mgcp_stat.h>
 #include <osmocom/mgcp/mgcp_msg.h>
 #include <osmocom/mgcp/mgcp_endp.h>