Mixed changes

- Added automatic utcb map/prefaulting of forked tasks for fs0
  so that it does not need to explicitly request those tasks from mm0.
  Eliminating fs0 requests to mm0 reduce deadlock possibilities.

- Replaced kmalloc with a public malloc implementation because of a bug in kmalloc.
- Fixed a kfree bug. default_release_pages was trying to free page_array pages.

tasks/mm0/include/task.h

@@ -101,5 +101,6 @@ void init_pm(struct initdata *initdata);
 
 struct tcb *task_create(struct task_ids *ids, unsigned int flags);
 int send_task_data(l4id_t requester);
+void task_map_prefault_utcb(struct tcb *mapper, struct tcb *owner);
 
 #endif /* __TASK_H__ */