Issue 4125 - [emscripten] Convert filter classes to C++

compiled/intrusive_ptr.h

 // Parts of this code have been copied from boost/smart_ptr/intrusive_ptr.hpp.
 //
 //  Copyright (c) 2001, 2002 Peter Dimov
 //
 // Distributed under the Boost Software License, Version 1.0. (See
 // accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt)
 
 #pragma once
 
@@ skipping 42 matching lines @@
   {
   }
 
   explicit intrusive_ptr(T* pointer)
       : mPointer(pointer)
   {
     // Raw pointers always had their reference count increased by whatever gave
     // us the pointer so we don't need to do it here.
   }
 
-  explicit intrusive_ptr(const intrusive_ptr& other)
+  intrusive_ptr(const intrusive_ptr& other)
       : mPointer(other.mPointer)
   {
     if (mPointer)
       mPointer->AddRef();
   }
 
-  explicit intrusive_ptr(intrusive_ptr&& other)
+  intrusive_ptr(intrusive_ptr&& other)
       : mPointer(other.mPointer)
   {
     other.mPointer = nullptr;
   }
 
   ~intrusive_ptr()
   {
     if (mPointer)
       mPointer->ReleaseRef();
   }
@@ skipping 110 matching lines @@
 inline bool operator==(const T* a, const intrusive_ptr<U>& b)
 {
   return a == b.get();
 }
 
 template<typename T, typename U>
 inline bool operator!=(const T* a, intrusive_ptr<U> const& b)
 {
   return a != b.get();
 }