ctnetlink updates take #3

Hi Harald!

Here follows the remaining set of patches that were held back for some different reasons.

[PATCH -1/4] kill the slipped through patch

[PATCH  1/4] implement get and zero counters
[PATCH  2/4] attribute sizes are size_t instead of int
[PATCH  3/4] skip sizechecking when not specified
[PATCH  4/4] add missing sizecheckings

cheers.

The dawn of the fourth age of Linux firewalling is coming; a time of
great struggle and heroic deeds -- J.Kadlecsik got inspired by J.Morris