fix compiler error

src/io/page_dmatrix-inl.hpp

@@ -18,7 +18,7 @@ struct RowBatchPage {
     utils::Assert(data_ != NULL, "fail to allocate row batch page");
     this->Clear();
   }
-  ~BinaryPage(void) {
+  ~RowBatchPage(void) {
     if (data_ != NULL) delete [] data_;
   }
   /*! 

src/utils/io.h

@@ -100,6 +100,7 @@ class ISeekStream: public IStream {
 /*! \brief implementation of file i/o stream */
 class FileStream : public ISeekStream {
  public:
+  explicit FileStream(void) {}
   explicit FileStream(FILE *fp) {
     this->fp = fp;
   }