kvm tools: Lookup symbol based on RIP for 'kill -3'

To make debugging easier, look up symbol from guest kernel image based on RIP
when user does 'kill -3' to the hypervisor.

Example output looks as follows:

  Code:
  -----
  rip: [<ffffffff812cb3a0>] delay_loop+30 (/home/penberg/linux/arch/x86/lib/delay.c:32)

Cc: Asias He <asias.hejun@gmail.com>
Cc: Avi Kivity <avi@redhat.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>