kernel/team: Convert Team linked-lists into DoublyLinkedLists.

They were hand-rolled singly-linked lists before. This adds 24 bytes
of size to the Team structure, but turns all the removal operations
in parent and process group into O(1) operations instead of O(N) ones.
Realistically, the Thread linked-lists should be converted as well,
but this is trickier due to interdependence on the Team structure.

headers/private/kernel/thread_types.h

@@ -220,14 +220,13 @@ struct Team : TeamThreadIteratorEntry<team_id>, KernelReferenceable,
 		AssociatedDataOwner {
 	DoublyLinkedListLink<Team>	global_list_link;
 	Team			*hash_next;		// next in hash
-	Team			*siblings_next;	// next in parent's list; protected by
-									// parent's fLock
+	DoublyLinkedListLink<Team> siblings_link; // protected by parent's fLock
 	Team			*parent;		// write-protected by both parent (if any)
 									// and this team's fLock
-	Team			*children;		// protected by this team's fLock;
-									// adding/removing a child also requires the
-									// child's fLock
-	Team			*group_next;	// protected by the group's lock
+	DoublyLinkedList<Team, DoublyLinkedListMemberGetLink<Team, &Team::siblings_link> > children;
+		// protected by this team's fLock;
+		// adding/removing a child also requires the child's fLock
+	DoublyLinkedListLink<Team> group_link; // protected by the group's lock
 
 	int64			serial_number;	// immutable after adding team to hash
 
@@ -667,9 +666,14 @@ private:
 
 
 struct ProcessGroup : KernelReferenceable {
-	struct ProcessGroup *next;		// next in hash
+	typedef DoublyLinkedList<Team,
+		DoublyLinkedListMemberGetLink<Team,
+			&Team::group_link> > TeamList;
+
+public:
+	struct ProcessGroup *hash_next;
 	pid_t				id;
-	BKernel::Team		*teams;
+	TeamList			teams;
 
 public:
 								ProcessGroup(pid_t id);