[mgcp] Make the mgcp_protocol generate a struct msgb*

Do not directly send data from inside the mgcp_protocol.c
implementation. Instead allocate and return a struct msgb*. The
caller can then either wrap that into the IPA protcol or directly
send it over the UDP socket.
diff --git a/openbsc/include/openbsc/mgcp.h b/openbsc/include/openbsc/mgcp.h
index 114b395..ee721d8 100644
--- a/openbsc/include/openbsc/mgcp.h
+++ b/openbsc/include/openbsc/mgcp.h
@@ -21,6 +21,11 @@
  *
  */
 
+#ifndef OPENBSC_MGCP_H
+#define OPENBSC_MGCP_H
+
+#include "msgb.h"
+
 #define RTP_PORT_DEFAULT 4000
 extern unsigned int rtp_base_port;
 
@@ -49,8 +54,9 @@
 }
 
 int mgcp_parse_config(const char *config_file, struct gsm_network *dummy_network);
-int mgcp_handle_message(int fd, struct msgb *msg, struct sockaddr_in *source);
-int mgcp_send_rsip(int fd, struct sockaddr_in *source);
+
+struct msgb *mgcp_handle_message(struct msgb *msg);
+struct msgb *mgcp_create_rsip(void);
 int mgcp_vty_init(void);
 
 /* endpoint managed */
@@ -60,3 +66,5 @@
 
 typedef int (*mgcp_change)(int endpoint, int state, int local_rtp, void *);
 void mgcp_set_change_cb(mgcp_change cb, void *data);
+
+#endif