PRISTINA (Reuters) - Kosovo Albanians will proclaim independence from Serbia on Sunday, ending a long chapter in the bloody breakup of Yugoslavia but cementing a bitter ethnic frontline in the Balkans. Kosovo will be the 6th state carved from the Serb-dominated federation since 1991, after Slovenia, Croatia, Macedonia, Bosnia and Montenegro, and the last to escape Serbia's embrace. The Serbs vow never to give up the land where their history goes back 1,000 years. They will reject independence in defiance of the Albanians and their Western backers and will keep their grip on strongholds in northern Kosovo, making the ethnic...