split invalidate_inodes()

Pull removal of fsnotify marks into generic_shutdown_super().
Split umount-time work into a new function - evict_inodes().
Make sure that invalidate_inodes() will be able to cope with
I_FREEING once we change locking in iput().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/internal.h

@@ -106,4 +106,5 @@ extern void release_open_intent(struct nameidata *);
  * inode.c
  */
 extern int get_nr_dirty_inodes(void);
+extern int evict_inodes(struct super_block *);
 extern int invalidate_inodes(struct super_block *);