Merge pull request #19 from simonkim/vgic

Vgic - Virtual IRQ Test code in vgic.c and bmguest/
vgic: guest context switch saves/restores VGIC status.
timer: multiple callbacks up to 8 per channel using timer_add_callback() api function
Merge branch 'proto2' of https://github.com/kesl/khypervisor into proto2
vgic: guest context switch saves/restores VGIC status.
vgic test code : tests_gic_timer.c, injects virq 30 to the current guest every timer_sched tick