firewall3: update to git head

  - Use weak references for instantiating libext*.a matches, makes fw3 independant from the compile time features of iptables
  - Do not leak memory when processing rules with unknown targets or matches

git-svn-id: svn://svn.openwrt.org/openwrt@36698 3c298f89-4303-0410-b956-a3cf2f4a3e73