bug#17820: sha1sum bug: bad reporting on filenames with "\"

[Morhold]

How to reproduce:

~> touch "a\b"

~> ls "a\b"
a\b

~> sha1sum "a\b"
\da39a3ee5e6b4b0d3255bfef95601890afd80709  a\\b

~> sha1sum --version
sha1sum (GNU coreutils) 8.13

~> lsb_release -ds
Ubuntu 12.04.4 LTS