SSA generates ACALL assembly with the target in a *Sym.
The old compiler generates both that *Sym and a *Node.
Use the *Sym to print the live info so it works with both compilers.

Change-Id: I0b12a161f83e76638604358c21b9f5abb31ce950
Reviewed-on: https://go-review.googlesource.com/16432
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>