This patch improves the overrun handling. The logic behind this patch
consists of two steps:

1) duplicate the netlink buffer size if the size does not goes after the
 upper boundary.
2) scheduling a resynchronization (in two seconds) with the kernel
conntrack table if we hit ENOBUFS. During the resynchronization, the
NFCT plugin dumps the current table and purges the objects that do not
exist anymore.

This patch also introduces two new clauses, the
netlink_socket_buffer_size and netlink_socket_buffer_maxsize that set
the size of the netlink socket buffer.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

-- 
"Los honestos son inadaptados sociales" -- Les Luthiers