6relayd: Rewrite init-script logic

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35133 3c298f89-4303-0410-b956-a3cf2f4a3e73
ipv6-support: don't use disable_ipv6

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35134 3c298f89-4303-0410-b956-a3cf2f4a3e73
odhcp6c: Add preliminary proto-handler

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35135 3c298f89-4303-0410-b956-a3cf2f4a3e73