Merge branch 'mcast'

Nicolas Dichtel says:

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The goal of this serie is to add the support of proxy multicast, ie being able
to build a static multicast tree. In other words, it adds the support of (*,G)
mf[6]c entries.

v2: use INADDR_ANY instead of 0 for IPv4 addresses
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Signed-off-by: David S. Miller <davem@davemloft.net>