This allows creation of initramfs images which contain a Live system.
The primary use for this is keeping very large initramfs-based systems
(e.g. anaconda, the Fedora installer) compressed in-memory, by using a
compressed filesystem image like squashfs or btrfs.
dmsquash-live-genrules.sh will initqueue dmsquash-live-root itself
(rather than making udev rules) if the given live "device" is actually
an existing, plain file.
parse-dmsquash-live.sh will only accept paths that end in ".img".
dmsquash-live-root will only handle images named "*squashfs.img",
"*ext3fs.img", or "*btrfs.img".
Fedora/Red Hat live images are implemented as an ext3fs inside of
a squashfs. Writability is achieved with a device-mapper snapshot
on top of that.
This gives the basic support without a lot of things like persistent
overlays, iso md5sum checking, etc and also with a new basic syntax
that has to be specified as root=live:LABEL=...