[NETFILTER]: nf_conntrack: split out protocol handling

This patch splits out L3/L4 protocol handling into its own file
nf_conntrack_proto.c

Signed-off-by: Martin Josefsson <gandalf@wlug.westbo.se>
Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --cc net/netfilter/Makefile
Simple merge

diff --cc net/netfilter/nf_conntrack_core.c
Simple merge

diff --cc net/netfilter/nf_conntrack_proto.c
Simple merge

diff --cc net/netfilter/nf_conntrack_standalone.c
Simple merge