message: Handle the HPM 'serfs' pop type
diff: @@ -126,6 +126,11 @@ Vic2::Province::Province(const std::string& numberString, std::istream& theStrea
  std::shared_ptr<Pop> pop = std::make_shared<Pop>(popType, theStream);
  pops.push_back(pop);
  });
  + registerKeyword(std::regex("serfs"), [this](const std::string& popType, std::istream& theStream)
  + {
  + std::shared_ptr<Pop> pop = std::make_shared<Pop>(popType, theStream);
  + pops.push_back(pop);
  + });
  // ignored items
  registerKeyword(std::regex("name"), commonItems::ignoreItem);
  