Avoid Using IStream::SetSize to Extend a Stream

When writing to streams, it is sometimes necessary to enlarge them because their initial size is no longer sufficient. Use the OLE method IStream::Write to accomplish this rather than IStream::SetSize. IStream::Write automatically extends the stream, making IStream::SetSize unnecessary. Calling IStream::Write without IStream::SetSize can be up to three times faster than making the SetSize call prior to Write.