kvm tools: Emulate RTC to fix system time in guests

kvm tools: Emulate RTC to fix system time in guests

This patch fixes system time in guests by implementing proper CMOS RTC clock
support.

  # Before:

  sh-2.05b# date
  Fri Aug  7 04:02:01 UTC 2009

  # After:

  sh-2.05b# date
  Thu Apr 28 19:12:21 UTC 2011

Cc: Asias He <asias.hejun@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Prasad Joshi <prasadjoshi124@gmail.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>