So, after the patch struct pid will look as:

struct pid {
        struct pstree_item *item;
        pid_t real;
        int state;
        struct {
                pid_t virt;
                struct rb_node node;
        } ns[1];
};

travis-ci: success for Make pstree_item::pid allocated dynamically
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>