Replace OStream with std::ostream.

src/compiler/node.cc

Index: src/compiler/node.cc
diff --git a/src/compiler/node.cc b/src/compiler/node.cc
index 7df736ee129471af9f291adf32d1163395e2c599..a64c8816dcbec6700d8ddf37d8f6a2b469aa4eb8 100644
--- a/src/compiler/node.cc
+++ b/src/compiler/node.cc
@@ -42,10 +42,12 @@ Node* Node::FindProjection(size_t projection_index) {
 }
 
 
-OStream& operator<<(OStream& os, const Operator& op) { return op.PrintTo(os); }
+std::ostream& operator<<(std::ostream& os, const Operator& op) {
+  return op.PrintTo(os);
+}
 
 
-OStream& operator<<(OStream& os, const Node& n) {
+std::ostream& operator<<(std::ostream& os, const Node& n) {
   os << n.id() << ": " << *n.op();
   if (n.op()->InputCount() != 0) {
     os << "(";