FULLCONENAT target patch for OpenWrt firewall3

Replaces firewall3's MASQUERADE target with FULLCONENAT

Depends

https://github.com/LGA1150/openwrt-fullconenat

Compile

# Download fullconenat.patch to package/network/config/firewall/patches/
mkdir package/network/config/firewall/patches
wget -P package/network/config/firewall/patches/ https://github.com/LGA1150/fullconenat-fw3-patch/raw/master/fullconenat.patch
# Patch LuCI
pushd feeds/luci
wget -O- https://github.com/LGA1150/fullconenat-fw3-patch/raw/master/luci.patch | git apply
popd
# Configure, select iptables-mod-fullconenat
make menuconfig
# Compile firewall3 only
make package/firewall/compile V=s
# or compile the whole image
make V=s