Pull up following revision(s) (requested by pgoyette in ticket #436):
distrib/sets/lists/modules/mi: revision 1.112
sys/modules/Makefile: revision 1.196
sys/modules/ip_ecn/Makefile: revision 1.1
sys/modules/if_gif/Makefile: revision 1.3
sys/net/if_gif.c: revision 1.136
sys/netinet/ip_ecn.c: revision 1.17
Split ip_ecn code into its own module, so it can be shared between
gif(4), stf(4), and ipsec(4).  Without this, loading the if_gif
module can result in redefined global symbols if either ipsec(4) or
stf(4) but not gif(4) is built into the kernel.
Fixes PR kern/52795 (as reported by martin@ via irc).

(snj)