vgic: guest context switch saves/restores VGIC status.
Merge pull request #20 from simonkim/proto2

timer: multiple callbacks up to 8 per channel using timer_add_callback()...
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
Merge branch 'proto2' of https://github.com/kesl/khypervisor into vgic
context: new api context_switchto() and context_perform_switch(), context_switch_to_next_guest() removed. added trap.c and sched_policy.c. schedule: new api scheduler_schedule() for default 'to next guest' behavior