message: api: make sure the opaque cswy engine structure has a vtable, otherwise sizes don't match.
diff: NWN_API_PROLOGUE(CassowarySolverEngineStructure)
  #endif
  +template<typename T>
  +struct SharedPtrEngineStructure
  +{
  + std::shared_ptr<T> m_shared;
  + virtual ~SharedPtrEngineStructure() {}
  +};
  -
  -
  -struct CassowarySolverEngineStructure
  +struct CassowarySolverEngineStructureShared;
  +struct CassowarySolverEngineStructure : public SharedPtrEngineStructure<CassowarySolverEngineStructureShared>
  {
  - std::shared_ptr<void*> m_shared;
  -
  + virtual ~CassowarySolverEngineStructure() {}
  #ifdef NWN_CLASS_EXTENSION_CassowarySolverEngineStructure
  NWN_CLASS_EXTENSION_CassowarySolverEngineStructure
  