ext4: enable acls and user_xattr by default

There's no good reason to require the extra step of providing
a mount option for acl or user_xattr once the feature is configured
on; no other filesystem that I know of requires this.

Userspace patches have set these options in default mount options,
and this patch makes them default in the kernel.  At some point
we can start to deprecate the options, perhaps.

For now I've removed default mount option checks in show_options()
to be explicit about what's set, since it's changing the default,
but I'm open to alternatives if desired.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>