server: entities private data allocation moved to server library

This is required for compatibility with Clang. Thanks to SamVanheer for the idea.

server/cbase.h

@@ -484,19 +484,19 @@ class CBaseEntity
 
 	virtual void MoveDone( void ) { if( m_pfnMoveDone )(this->*m_pfnMoveDone)(); };
 
-	// allow engine to allocate instance data
-	void *operator new( size_t stAllocateBlock, entvars_t *pev )
+	void *operator new(size_t stAllocateBlock)
 	{
-		return (void *)ALLOC_PRIVATE(ENT(pev), static_cast<int>(stAllocateBlock));
+		void *block = ::operator new(stAllocateBlock);
+		std::memset(block, 0, stAllocateBlock);
+		return block;
 	};
 
-	// don't use this.
-#if _MSC_VER >= 1200 // only build this code if MSVC++ 6.0 or higher
-	void operator delete(void *pMem, entvars_t *pev)
+	// don't call delete on entities directly, tell the engine to delete it instead
+	void operator delete(void *pMem)
 	{
-		pev->flags |= FL_KILLME;
+		::operator delete(pMem);
 	};
-#endif
+
 	void UpdateOnRemove( void );
 
 	// common member functions
@@ -1081,7 +1081,8 @@ template <class T> T * GetClassPtr( T *a )
 	if (a == NULL) 
 	{
 		// allocate private data 
-		a = new(pev) T;
+		a = new T;
+		pev->pContainingEntity->pvPrivateData = a; // replicate the ALLOC_PRIVATE engine function's behavior
 		a->pev = pev;
 	}
 	return a;
@@ -1101,7 +1102,8 @@ template <class T> T * GetClassPtr( T *newEnt, const char *className )
 	if (newEnt == NULL) 
 	{
 		// allocate private data 
-		newEnt = new(pev) T;
+		newEnt = new T;
+		pev->pContainingEntity->pvPrivateData = newEnt; // replicate the ALLOC_PRIVATE engine function's behavior
 		newEnt->pev = pev;
 	}
 	newEnt->SetClassname( className );

server/dll_int.cpp

@@ -548,7 +548,8 @@ void OnFreeEntPrivateData( edict_s *pEdict )
 	{
 		CBaseEntity *pEntity = CBaseEntity::Instance(pEdict);
 		pEntity->UpdateOnRemove();
-		pEntity->~CBaseEntity();
+		delete pEntity;
+		pEdict->pvPrivateData = nullptr; // zero this out so the engine doesn't try to free it again
 	}
 }