SKOPJE, Macedonia — Macedonians have had a country to call their own for less than three decades. Now, the citizens of one of Europe’s youngest countries are being asked to weigh matters of national identity and national interest as they decide a fundamental question: what their homeland will be called. A referendum set for Sunday seeks voter support for changing the Balkan nation’s name to North Macedonia. Greece has agreed to drop long-standing objections to neighboring Macedonia joining NATO and eventually becoming a member of the European Union if the new name is approved.