Bugfixes, enhancements

- Fixed an important bug with shadow object handling.
  When a shadow is dropped, if there are references left
  to it, both the object in front and dropped object becomes
  a shadow of the original object underneath. We had thought
  of this case but had not increase the shadow count.

- Added a test mechanism that tests the number of objects,
  vmfiles, shadows etc. by first counting them and trying to
  reach the same number by other means, i.e. per-object-shadow counts.
  It discovered a plethora of bugs.

- Added new set of functions to register objects, files and tasks
  globally with the pager, these functions introduce a refcount as
  well as adding structures to linked lists.

- fork/exit now seems to work stably i.e. no negative shadow counts etc.

tasks/mm0/src/clone.c

@@ -100,7 +100,7 @@ int sys_fork(struct tcb *parent)
 	vfs_notify_fork(child, parent);
 
 	/* Add child to global task list */
-	task_add_global(child);
+	global_add_task(child);
 
 	/* Start forked child. */
 	l4_thread_control(THREAD_RUN, &ids);
@@ -145,7 +145,7 @@ int sys_clone(struct tcb *parent, void *child_stack, unsigned int flags)
 	vfs_notify_fork(child, parent);
 
 	/* Add child to global task list */
-	task_add_global(child);
+	global_add_task(child);
 
 	/* Start forked child. */
 	printf("%s/%s: Starting forked child.\n", __TASKNAME__, __FUNCTION__);