This patch introduces IPC namespaces, which allow to create isolated IPC 
users or containers.
Introduces CONFIG_IPC_NS and ipc_namespace structure.
It also uses current->ipc_ns as a pointer to current namespace, which 
reduces places where additional argument to functions should be added.

Signed-Off-By: Pavel Emelianov <xemul@openvz.org>
Signed-Off-By: Kirill Korotaev <dev@openvz.org>