gem5 requires armv7, and we learnt that the versatiledb we were using
was pre-v7.
We could have moved to -M vexpress-*, but in the end decided to go for
-M virt due to its simpliciy, and uniformity with aarch64.
platform_device: does not work anymore and was removed, since it was tied
to versatilepb.
We left a mention on the README and removed all in tree source. The QEMU
patch is still left as it was.
As a consequence, the linux tree had no other patches, and we now use
vanilla linux by default, which is a great thing for reproducibility.
Another consequence is the /poweroff.out works for arm -M virt,
and we removed all mentions of the problem.
Document that X11 mouse is not moving.
Convert x='' to x= on all scripts, and also fix case ;; indentations.
Add dummy value to QEMU's -trace enable= to prevent warning.
Expand built-in package choice rationale.
