tasksel now allows selecting the desktop, and d-i has dropped the boot
menu desktop selection, so we no longer need to have desktop boot
menus on CDs.
CD images for specific desktops (xfce/kde/mate/etc) should still
override the default tasksel desktop.
The code was assuming that the first line of output was something like
this (and this is the case of the cd builder machine that uses a custom
built xorriso):
> GNU xorriso 1.2.6 : RockRidge filesystem manipulator, libburnia project.
But the output of the version packaged in Debian does not have the GNU
string:
> xorriso 1.3.2 : RockRidge filesystem manipulator, libburnia project.
We fix this issue by extracting the version from the line starting with
"xorriso version" which does not have this discrepancy.
When making a custom server netinstall ISO, it may be desired to not
have MS Windows files. Unfortunately there's currently no check for
loadlin.exe, so install.bat gets created regardless. Fix this.
debian-cd currently expects there to always be isolinux/desktop/*
files and a dtmenu.cfg file, failing if they are missing. Make it so
debian-cd can cope whether those files are present or not.