enable v8plus_call to be used in any thread

*** 27,39 ****
  
  #if NODE_MINOR_VERSION > 7 || NODE_MAJOR_VERSION > 0
  #define NODE_MAKECALLBACK_RETURN
  #endif
  
- extern "C" boolean_t v8plus_in_event_thread(void);
- extern "C" void v8plus_crossthread_init(void);
- 
  namespace v8plus {
  
  class ObjectWrap;
  
  class ObjectWrap : public node::ObjectWrap {
--- 27,36 ----