dump: Add futex robust list dumping v3

This patch introduces ThreadCoreEntry protobuf structure which is to carry
thread-specific arch-independent information.

Now put there the c/r futex robust lists.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>