BRUSSELS — The Czech Republic, Hungary, Poland and Slovakia announced Thursday that they plan to spend around $41 million to beef up European Union borders as they come under pressure for refusing to accept refugee quotas. The countries — known as the Visegrad Four — have been criticized for failing to show solidarity with Greece and Italy, where tens of thousands of migrants have landed after crossing the Mediterranean or Aegean Seas. The issue of migrants and refugees was high on the agenda of a two-day EU summit in Brussels that started Thursday — and some saw the border funding move by the four nations as a cynical ploy to avoid accepting refugee quotas.