[dev.ssa] cmd/compile: give GetClosurePtr pointer type

If the closure pointer gets spilled, we need to spill it with
pointer type to make stack copy and GC happy.

Change-Id: Ic108748e6b9caecd45522141f02c9422567376e3
Reviewed-on: https://go-review.googlesource.com/16363
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/gc/ssa.go

@@ -2335,7 +2335,7 @@ func (s *state) addr(n *Node, bounded bool) *ssa.Value {
 		return s.newValue2(ssa.OpAddPtr, p.Type, p, s.constIntPtr(Types[TUINTPTR], n.Xoffset))
 	case OCLOSUREVAR:
 		return s.newValue2(ssa.OpAddPtr, Ptrto(n.Type),
-			s.entryNewValue0(ssa.OpGetClosurePtr, Types[TUINTPTR]),
+			s.entryNewValue0(ssa.OpGetClosurePtr, Ptrto(Types[TUINT8])),
 			s.constIntPtr(Types[TUINTPTR], n.Xoffset))
 	case OPARAM:
 		p := n.Left