socket export cleanup (1)

[Joerg Sonnenberger]

Hi all,
the patch at http://leaf.dragonflybsd.org/~joerg/no_gencnt.diff removes
the userland visible part of the socket generation counting. That made
the much more difficult and in case we really want to notify the userland
about intermediate destruction of sockets, we should use an error code
for sysctl like EAGAIN instead.

Once this is in the tree, the larger generic socket export patch will
follow.

@Matt: Did you slip the Stable tag in the mean time? I'd like to have
this ABI breakage finished in -CURRENT first.

Joerg