batman-adv: upgrade package to latest release 2019.1

batman-adv: upgrade package to latest release 2019.1

* support latest kernels (3.16 - 5.1)
* coding style cleanups and refactoring
* implement meshif, hardif and vlan config interface via netlink
* snoop DHCP ACKs to improve DAT cache efficiency
* bugs squashed:

  - avoid potential reference counter underflows and use-after free errors for
    several objects
  - fix GCC warning when B.A.T.M.A.N. V is build in but cfg80211 is not
    available
  - reject too small VLAN packets before they are processed further

Signed-off-by: Sven Eckelmann <sven@narfation.org>