Merge branch 'netlink-auto-integers'

Jakub Kicinski says:

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netlink: add variable-length / auto integers

Add netlink support for "common" / variable-length / auto integers
which are carried at the message level as either 4B or 8B depending
on the exact value. This saves space and will hopefully decrease
the number of instances where we realize that we needed more bits
after uAPI is set is stone. It also loosens the alignment requirements,
avoiding the need for padding.

This mini-series is a fuller version of the previous RFC:
https://lore.kernel.org/netdev/20121204.130914.1457976839967676240.davem@davemloft.net/
No user included here. I have tested (and will use) it
in the upcoming page pool API but the assumption is that
it will be widely applicable. So sending without a user.
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Signed-off-by: David S. Miller <davem@davemloft.net>