Changes

A process of restoring has a few global synchronization points:

A process of restoring has a few global synchronization points:

* CR_STATE_FORKING - Create tasks and restore group leaders.

* CR_STATE_RESTORE_PGID - Restore group IDs. Group leaders should exist in this moment and all helpers should be alive.

| <code>CR_STATE_FORKING</code> || Create tasks and restore group leaders

* CR_STATE_RESTORE - Wait helpers and restore a most part of resources. If anyone segfauls, its parent gets SIGCHLD and notify criu about that.

* CR_STATE_RESTORE_SIGCHLD - Restore SIGCHLD handlers

| <code>CR_STATE_RESTORE_PGID</code> || Restore group IDs. Group leaders should exist in this moment and all helpers should be alive

* CR_STATE_COMPLETE - All handlers were restored, origin processes can be resumed.

| <code>CR_STATE_RESTORE</code> || Wait helpers and restore a most part of resources. If anyone segfauls, its parent gets SIGCHLD and notify criu about that

| <code>CR_STATE_RESTORE_SIGCHLD</code> || Restore <code>SIGCHLD</code> handlers

| <code>CR_STATE_COMPLETE</code> || All handlers were restored, origin processes can be resumed.