daemon: Allow xorriso as an alternative to isoinfo.

Currently the guestfs_isoinfo and guestfs_isoinfo_device APIs run
isoinfo inside the appliance to extract the information.

isoinfo is part of genisoimage which is somewhat dead upstream.
xorriso is supposedly the new thing.  (For a summary of the situation
see: https://wiki.debian.org/genisoimage).

This commit rewrites the parsing from C to OCaml to make it easier to
deal with, and allows you to use either isoinfo or xorriso.

Mostly the same fields are available from either tool, but xorriso is
a bit more awkward to parse.

appliance/packagelist.in

@@ -45,6 +45,7 @@ ifelse(REDHAT,1,
   syslinux-extlinux
   systemd              dnl for /sbin/reboot and udevd
   vim-minimal
+  xorriso              dnl alternative for genisoimage
   xz
   zfs-fuse
 )
@@ -84,6 +85,7 @@ dnl iproute has been renamed to iproute2
   systemd                   dnl alternative for /sbin/reboot
   ufsutils
   vim-tiny
+  xorriso                   dnl alternative for genisoimage
   xz-utils
   zfs-fuse
   uuid-runtime