* Fixes and debugging help for the #VE sanity check.  Also disable
  it by default, even for CONFIG_DEBUG_KERNEL, because it was found
  to trigger spuriously (most likely a processor erratum as the
  exact symptoms vary by generation).

* Avoid WARN() when two NMIs arrive simultaneously during an NMI-disabled
  situation (GIF=0 or interrupt shadow) when the processor supports
  virtual NMI.  While generally KVM will not request an NMI window
  when virtual NMIs are supported, in this case it *does* have to
  single-step over the interrupt shadow or enable the STGI intercept,
  in order to deliver the latched second NMI.

* Drop support for hand tuning APIC timer advancement from userspace.
  Since we have adaptive tuning, and it has proved to work well,
  drop the module parameter for manual configuration and with it a
  few stupid bugs that it had.