[BL/IO] Move internal function to private section.

BaseLib/IO/XmlIO/Qt/XMLQtInterface.h

@@ -36,9 +36,6 @@ public:
     virtual int readFile(const QString &fileName);
 
 protected:
-    /// Check if the given xml-file is valid considering the schema-file used in the constructor
-    int isValid() const;
-
     /// Checks if a hash for the given data file exists to skip the time-consuming validation part.
     /// If a hash file exists _and_ the hash of the data file is the same as the content of the hash file the validation is skipped
     /// If no hash file exists, the xml-file is validated and a hash file is written if the xml-file was valid.
@@ -47,6 +44,10 @@ protected:
     /// Caches the actual file contents when reading.
     QByteArray _fileData;
 
+private:
+    /// Check if the given xml-file is valid considering the schema-file used in
+    /// the constructor
+    int isValid() const;
 
 private:
     /// The actual file name when reading.