rst_mem_alloc rules might move previously allocated
blocks which means we can't reuse previously allocated
pointer if new block is created. Thus remember pointers
positions where needed and adjust them accordingly.

https://github.com/xemul/criu/issues/97Reported-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>