volume_id: add squashfs detection

function                                             old     new   delta
volume_id_probe_squashfs                               -      74     +74
fs1                                                   12      16      +4

Signed-off-by: Sven-Göran Bergh <sgb@systemasis.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
4 files changed