MFC r249846:

When rebooting (exiting) from the BTX loader, make sure to restore the
GDT from the correct segment, otherwise a triple fault would be caused.
In some virtual environments (VMware, VirtualBox, etc) this could lead
to a unhandled error or hang in the guest emulation software.

Thanks to avg and jhb for a few hints in the right direction.

Noticed by:	Jeremy Chadwick <jdc@koitsu.org> (and many others)


git-svn-id: svn+ssh://svn.freebsd.org/base/stable/6@250151 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Tidy up some CVS workarounds.


git-svn-id: svn+ssh://svn.freebsd.org/base/stable/6@250544 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f