[INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h

To help in reducing the number of include dependencies, several files were
touched as they were getting needed headers indirectly for stuff they use.

Thanks also to Alan Menegotto for pointing out that net/dccp/proto.c had
linux/dccp.h include twice.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip.h

@@ -24,14 +24,10 @@
 
 #include <linux/config.h>
 #include <linux/types.h>
-#include <linux/socket.h>
 #include <linux/ip.h>
 #include <linux/in.h>
-#include <linux/netdevice.h>
-#include <linux/inetdevice.h>
-#include <linux/in_route.h>
-#include <net/route.h>
-#include <net/arp.h>
+
+#include <net/inet_sock.h>
 #include <net/snmp.h>
 
 struct sock;
@@ -75,6 +71,13 @@ extern rwlock_t ip_ra_lock;
 
 #define IP_FRAG_TIME	(30 * HZ)		/* fragment lifetime	*/
 
+struct msghdr;
+struct net_device;
+struct packet_type;
+struct rtable;
+struct sk_buff;
+struct sockaddr;
+
 extern void		ip_mc_dropsocket(struct sock *);
 extern void		ip_mc_dropdevice(struct net_device *dev);
 extern int		igmp_mc_proc_init(void);
@@ -184,6 +187,8 @@ extern int sysctl_ip_dynaddr;
 extern void ipfrag_init(void);
 
 #ifdef CONFIG_INET
+#include <net/dst.h>
+
 /* The function in 2.2 was invalid, producing wrong result for
  * check=0xFEFF. It was noticed by Arthur Skawina _year_ ago. --ANK(000625) */
 static inline