ext4: ignore mount options supported by ext2/3 (but have since been removed)

Users who tried to use the ext4 file system driver is being used for
the ext2 or ext3 file systems (via the CONFIG_EXT4_USE_FOR_EXT23
option) could have failed mounts if their /etc/fstab contains options
recognized by ext2 or ext3 but which have since been removed in ext4.

So teach ext4 to recognize them and give a warning that the mount
option was removed.

Report: https://bbs.archlinux.org/profile.php?id=33804



Signed-off-by: Tom Gundersen <teg@jklm.no>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Thomas Baechler <thomas@archlinux.org>
Cc: Tobias Powalowski <tobias.powalowski@googlemail.com>
Cc: Dave Reisner <d@falconindy.com>