rcu hashtable

This generic hash table does not follow STL conventions, since using an
iterator is difficult where things can change under your feet.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
tests: add test for rcu_hashtable

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
net: use rcu_hashtable in net channel classifier

Reduce overhead in creating a tcp connection from O(existing connection count)
to O(1).

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>