[dev.ssa] cmd/compile/internal/gc: Interpret init list of OFOR conditions

Fixes build.  Some variables are initialized in this list.

Q: How do we tell that we've included all the required Ninit lists?

Change-Id: I96b3f03c291440130303a2b95a651e97e4d8113c
Reviewed-on: https://go-review.googlesource.com/11542Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

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

@@ -380,6 +380,7 @@ func (s *state) stmt(n *Node) {
 			s.Unimplementedf("cond n.Left == nil: %v", n)
 		}
 		s.startBlock(bCond)
+		s.stmtList(n.Left.Ninit)
 		cond := s.expr(n.Left)
 		b = s.endBlock()
 		b.Kind = ssa.BlockIf