The per-thread information requires own space in parasite data.
In particular we will keep the blocked signals bound to thread
pids.

For this sake the caller need to provide the parasite how many
threads will be used to calculate space.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>