net: Convert LIMIT_NETDEBUG to net_dbg_ratelimited

Use the more common dynamic_debug capable net_dbg_ratelimited
and remove the LIMIT_NETDEBUG macro.

All messages are still ratelimited.

Some KERN_<LEVEL> uses are changed to KERN_DEBUG.

This may have some negative impact on messages that were
emitted at KERN_INFO that are not not enabled at all unless
DEBUG is defined or dynamic_debug is enabled.  Even so,
these messages are now _not_ emitted by default.

This also eliminates the use of the net_msg_warn sysctl
"/proc/sys/net/core/warnings".  For backward compatibility,
the sysctl is not removed, but it has no function.  The extern
declaration of net_msg_warn is removed from sock.h and made
static in net/core/sysctl_net_core.c

Miscellanea:

o Update the sysctl documentation
o Remove the embedded uses of pr_fmt
o Coalesce format fragments
o Realign arguments

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index 6d16eb0..8ab1989 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -272,10 +272,9 @@
 				ipv6_rearrange_destopt(iph, exthdr.opth);
 		case NEXTHDR_HOP:
 			if (!zero_out_mutable_opts(exthdr.opth)) {
-				LIMIT_NETDEBUG(
-					KERN_WARNING "overrun %sopts\n",
-					nexthdr == NEXTHDR_HOP ?
-						"hop" : "dest");
+				net_dbg_ratelimited("overrun %sopts\n",
+						    nexthdr == NEXTHDR_HOP ?
+						    "hop" : "dest");
 				return -EINVAL;
 			}
 			break;