goldfish: Enable multinetwork kernel features.

These are required for Android L and beyong. The following changes
were generated by doing the following:

 1) For each CPU architecture, append the following to its _defconfig
    file:

	CONFIG_IPV6=y
	CONFIG_IPV6_MULTIPLE_TABLES=y
	CONFIG_IP_ADVANCED_ROUTER=y
	CONFIG_IP_MULTIPLE_TABLES=y
	CONFIG_NETFILTER=y
	CONFIG_NETFILTER_ADVANCED=y
	CONFIG_NETFILTER_XTABLES=y
	CONFIG_NETFILTER_XT_MARK=y
	CONFIG_NETFILTER_XT_TARGET_MARK=y
	CONFIG_IP_NF_IPTABLES=y
	CONFIG_IP_NF_MANGLE=y
	CONFIG_IP6_NF_IPTABLES=y
	CONFIG_IP6_NF_MANGLE=y

  2) For each CPU architecture, run:

      $AOSP/external/qemu/distrib/rebuild-kernel.sh --arch=$ARCH --savedefconfig

  The --savedefconfig option ensures the _defconfig is modified to only
  contain the minimal amount of changes required, and removes un-necessary
  definitions too.

BUG=17516983

Signed-off-by: David 'Digit' Turner <digit@android.com>