Fix Windows 2000, XP, Vista and Windows 7 Clock Drift (ACPI) even with clock=realtime on Bochs.

[youself64github]

I want to fix clock drift even with clock=realtime enabled for Windows 2000, XP, Vista and Windows 7 guests (ACPI enabled) in Bochs. though it doesn't suffer clock drift on Windows 2000 and XP guests and older Windows guests with Standard PC instead of ACPI PC, Windows 8 and later guests with clock=realtime enabled on Bochs.

[Vort]

I confirm this problem with Windows 2000 and clock: sync=realtime, time0=local, rtc_sync=0:
When Windows is loading, time goes slower; when loading is finished, time goes faster. rtc_sync=1 makes no difference.