add hyper-v enlightments for windows guests

add hyper-v enlightments for windows guests

This add special hyper-v cpu flags for windows guests.

This improve performance and avoid some bsod related to timer.

(I currently disable the hv_vapic flag because I can't get it working).

I have tested all theses flags with: win2003, win2008R2, winxp, linux debian 64bit, on intel and amd physicals processor

It doesn't break live migration, because new cpu flags are not see by guests until a vm reset.

Signed-off-by: Alexandre Derumier <aderumier@odiso.com>