tune2fs: allow enabling casefold feature after fs creation

tune2fs: allow enabling casefold feature after fs creation

The main reason we didn't allow this before was because !CASEFOLDED
directories were expected to be normalized().  Since this is no longer
the case, and as long as the encrypt feature is not enabled, it should
be safe to enable this feature.

Disabling the feature is trickier, since we need to make sure there are
no existing +F directories in the filesystem.  Leave that for a future
patch.

Also, enabling strict mode requires some filesystem-wide verification,
so ignore that for now.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Arnaud Ferraris <arnaud.ferraris@collabora.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>