This requires some exlanations

 - Since we use protobuf data in restorer
   code we need to carry a copy of appropriate
   PB entities in resident memory. For this
   sake task_restore_core_args and thread_restore_args
   were significantly reworked. In short -- the caller
   code fills PB structures into task arguments space.

v3:
 - Combine everything arch related to thread_info field,
   and make it optional
 - Drop "version" field from message, we check version in
   another specific message
 - Don't forget to call core_entry__free_unpacked where needed
 - We continue dumping FPU state, still it's not yet restored

v4:
 - Don't carry task_core_entry and task_kobs_ids_entry for
   threads, and yield error if present in image.

v5:
 - Allocate core_entry depending on type of task being dumped
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>