More work on moving engine into dlmalloc heap

luprex/core/cpp/streambuffer.cpp

@@ -504,18 +504,18 @@ public:
     }
 };
 
-class StreamBufferOStream : public eng::ostream {
+class StreamBufferOStream : public std::ostream {
 private:
     StreamBufferWriter writer_;
 public:
-    StreamBufferOStream(StreamBuffer *t) : eng::ostream(nullptr), writer_(t) {
+    StreamBufferOStream(StreamBuffer *t) : std::ostream(nullptr), writer_(t) {
         rdbuf(&writer_);
     }
     virtual ~StreamBufferOStream() {
     }
 };
 
-eng::ostream &StreamBuffer::ostream() {
+std::ostream &StreamBuffer::ostream() {
     if (ostream_ == nullptr) {
         ostream_.reset(new StreamBufferOStream(this));
     }