autofile: Disallow by-value copies of CAutoFile

One might assume that CAutoFile would be ref-counted so that a copied object
would delay closing the underlying file until all copies have gone out of
scope. Since that's not the case with CAutoFile, explicitly disable copying.

src/serialize.h

@@ -1154,7 +1154,7 @@ public:
 
 
 
-/** RAII wrapper for FILE*.
+/** Non-refcounted RAII wrapper for FILE*.
  *
  * Will automatically close the file when it goes out of scope if not null.
  * If you're returning the file pointer, return file.release().
@@ -1162,6 +1162,10 @@ public:
  */
 class CAutoFile
 {
+private:
+    // Disallow copies
+    CAutoFile(const CAutoFile&);
+    CAutoFile& operator=(const CAutoFile&);
 protected:
     FILE* file;
 public: