xfs_scrub: warn about suspicious characters in directory/xattr names

xfs_scrub: warn about suspicious characters in directory/xattr names

Look for control characters and punctuation that interfere with shell
globbing in directory entry names and extended attribute key names.
Technically these aren't filesystem corruptions because names are
arbitrary sequences of bytes, but they've been known to cause problems
in the Unix environment so warn if we see them.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>