This actually does two things:

1. The parasite code writes to pages _or_ to pages_shared file himself based
   on a hint given from the main program. This avoids shared pages copying
   in finalize_core.

2. The private pages are moved out of the core file into a separate one. This
   avoids private pages copying in finalize_core.

The goal of this patch is a) to avoid pages copying at all (we still have
one on restore, but fixing this requires Andrey's work on shared memory
dumping) and b) make big blobs with pages be stored in separate files (I
have plans on its format rework and unification).
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>