This is to avoid long item->pid->ns[0].virt for vpid(item).

This is
1) for f in $(git grep -l 'ns\[0\]'); do
           sed -e 's/\([a-zA-Z0-9_]\+\)->pid->ns\[0\].virt/vpid(\1)/g' -i $f;
   done
2) adding of vpid() routine
3) some manual fixlets
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>