Merge branch 'igmp_mld_export'

Linus Lüssing says:

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Exporting IGMP/MLD checking from bridge code

The multicast optimizations in batman-adv are yet only usable and
enabled in non-bridged scenarios. To be able to support bridged setups
batman-adv needs to be able to detect IGMP/MLD queriers and reports on
mesh nodes without bridges, too. See the following link for details:

http://www.open-mesh.org/projects/batman-adv/wiki/Multicast-optimizations-listener-reports



To avoid duplicate code between the bridge and batman-adv, the IGMP/MLD
message validation code is moved from the bridge to the IPv4/IPv6 stack.

On the way, some refactoring to increase readability and to iron out
some subtle differences between the IGMP and MLD parsing code is done.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>