[mgcp] Include stdlib.h for abs.
diff --git a/openbsc/src/mgcp/mgcp_network.c b/openbsc/src/mgcp/mgcp_network.c
index e73b3a5..9852d8b 100644
--- a/openbsc/src/mgcp/mgcp_network.c
+++ b/openbsc/src/mgcp/mgcp_network.c
@@ -23,6 +23,7 @@
  */
 
 #include <string.h>
+#include <stdlib.h>
 #include <unistd.h>
 #include <endian.h>
 #include <errno.h>