operator== could be faster by checking node identity

Author: rressi

json11.cpp

@@ -302,6 +302,8 @@ const Json & JsonArray::operator[] (size_t i) const {
 bool Json::operator== (const Json &other) const {
  if (m_ptr->type() != other.m_ptr->type())
  return false;
+ if (m_ptr == other.m_ptr)
+ return true;
 
  return m_ptr->equals(other.m_ptr.get());
 }