Allow reassigning scoped_dohptr

Not being able to do it is too restrictive in practice and just forces
to use raw DOH pointers, which is not really less dangerous than adding
the assignment operator and reset() method to this class.

Source/Modules/c.cxx

@@ -37,7 +37,17 @@ public:
   ~scoped_dohptr() { Delete(obj_); }
 
   // This is an std::auto_ptr<>-like "destructive" copy ctor which allows to return objects of this type from functions.
-  scoped_dohptr(scoped_dohptr const& tmp) : obj_(tmp.release()) {}
+  scoped_dohptr(scoped_dohptr const& other) : obj_(other.release()) {}
+
+  // Same for the assignment operator.
+  scoped_dohptr& operator=(scoped_dohptr const& other) {
+    if (&other != this) {
+      Delete(obj_);
+      obj_ = other.release();
+    }
+
+    return *this;
+  }
 
   DOH* get() const { return obj_; }
 
@@ -47,12 +57,17 @@ public:
     return obj;
   }
 
+  void reset() {
+    if (obj_) {
+      Delete(obj_);
+      obj_ = NULL;
+    }
+  }
+
   operator DOH*() const { return obj_; }
 
 private:
-  scoped_dohptr& operator=(scoped_dohptr const&);
-
-  DOH* const obj_;
+  DOH* obj_;
 };
 
 // Helper class to output "begin" fragment in the ctor and "end" in the dtor.