ntdll:exception crashes some Windows 10

[Francois Gouget]

For future reference here is a summary of some additional tests I did 
with Paul:

* Setting all Dr* fields to 0 in dreg_handler() except Dr2 still causes 
  a crash. That's a buggy behavior.

* Moving the TestBot's w10pro64 VM to my box and running ntdll:exception 
  also leads to a crash. So that seems to indicate a host issue rather 
  than a guest-side Windows configuration issue.

* All hosts are running Debian 10 but combining my results with the 
  TestBot's we have the following matrix:

  kernel 4.19.0-12-amd64 + QEmu 1:3.1+dfsg-8+deb10u8 -> Works (w1064)
  kernel 5.8.0-0.bpo.2-amd64 + QEmu 1:5.0-14~bpo10+1 -> Works (w10pro64)
  kernel 4.19.0-11-amd64 + QEmu 1:5.0-14~bpo10+1     -> Crashes (my w10pro64)

  So maybe it's a 4.19.0.11 bug or QEmu 5.0 does not like 4.19 kernels. 
  I'll continue the tests when I can reboot.

-- 
Francois Gouget <fgouget at codeweavers.com>