Fix complie on FreeBSD 5.4 and AIX.

This is picked from commits

d9c26f3aeb
"ng_ipaddr.h must include netinet/in.h."

and
4e507881f3
"On AIX (for example) socklen_t is defined in sys/socket.h"

src/ipaddr/ng_ipaddr.c

@@ -14,9 +14,6 @@
 #include <netdb.h>
 #include <sys/types.h>
 #endif
-#include <sys/socket.h>
-
-#include <netinet/in.h>
 
 #include "ng_ipaddr.h"
 

src/ipaddr/ng_ipaddr.h

@@ -8,6 +8,9 @@
 #define NG_IPADDR_HDR
 #include "portab.h"
 
+#include <sys/socket.h>
+#include <netinet/in.h>
+
 #ifdef HAVE_ARPA_INET_H
 # include <arpa/inet.h>
 #else