look: consider blanks as directory characters

look: consider blanks as directory characters

This change introduces regression, but it seems better than to be
incompatible with "sort -d" if we assume that "sort -d" is the right
way how to prepare files for look(1).

It seems (from man page) that the original goal has been compatibility
with sort -d, but this feature has never been fully implemented.

Addresses: https://github.com/karelzak/util-linux/issues/284
Signed-off-by: Karel Zak <kzak@redhat.com>