[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>
diff --git a/include/net/icmp.h b/include/net/icmp.h
index 6cdebee..e7c3f20 100644
--- a/include/net/icmp.h
+++ b/include/net/icmp.h
@@ -20,12 +20,9 @@
 
 #include <linux/config.h>
 #include <linux/icmp.h>
-#include <linux/skbuff.h>
 
-#include <net/sock.h>
-#include <net/protocol.h>
+#include <net/inet_sock.h>
 #include <net/snmp.h>
-#include <linux/ip.h>
 
 struct icmp_err {
   int		errno;
@@ -38,6 +35,10 @@
 #define ICMP_INC_STATS_BH(field)	SNMP_INC_STATS_BH(icmp_statistics, field)
 #define ICMP_INC_STATS_USER(field) 	SNMP_INC_STATS_USER(icmp_statistics, field)
 
+struct dst_entry;
+struct net_proto_family;
+struct sk_buff;
+
 extern void	icmp_send(struct sk_buff *skb_in,  int type, int code, u32 info);
 extern int	icmp_rcv(struct sk_buff *skb);
 extern int	icmp_ioctl(struct sock *sk, int cmd, unsigned long arg);