[PATCH] x86-64: cleanup segments

Move __KERNEL32_CS up into the unused gdt entry.  __KERNEL32_CS is
used when entering the kernel so putting it first is useful when
trying to keep boot gdt sizes to a minimum.

Set the accessed bit on all gdt entries.  We don't care
so there is no need for the cpu to burn the extra cycles,
and it potentially allows the pages to be immutable.  Plus
it is confusing when debugging and your gdt entries mysteriously
change.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>