[Devel] [PATCH VZ9] hide unused field in thread_info

[Alexey Kuznetsov]

RHEL added this unused field by an unknown reason, apparently
brainlessy backporting some patch from mainstream.

It looks just as harmless waste of memory, but it is worse,
as tools like drgn interpret its presence as indicator that kernel
works according to rules of that mainstream kernel that
patch was borrowed from. The result - drgn becomes useless.

It is unreasonable to fix drgn as it will break it for
correct kernels. We could delete this unused field. But for now
it seems more clever to keep struct binary compatible,
only with the field renamed.

Signed-off-by: Alexey Kuznetsov <kuznet at acronis.com>