ns: Use ns_ prefix in routines

The routines are not per-task but per namespace rather.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
ns: ipc -- Add warning about ipc conversion.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
ns: ipc -- Add conversion of IPC variables

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>