Prettifyed the code exploiting inheritance rules

added missing comma, added missing `override`

--HG--
branch : minor

src/modules/filesystem/FileData.h

@@ -45,7 +45,7 @@ public:
 	virtual ~FileData();
 
 	// Implements Data.
-	Data *clone() const;
+	FileData *clone() const;
 	void *getData() const;
 	size_t getSize() const;