(Reuters) – Libya's two-month civil war spilled over the border into Tunisia, provoking outrage in the western neighbor, while rebels in Misrata said only NATO could halt the bombardment of the besieged city. The struggle between forces loyal to Libyan leader Muammar Gaddafi and rebels trying to end his more than four decades of rule drew in outsiders last month, as NATO began air strikes on government troops under a United Nations mandate. But on Thursday the fighting spilled over Libya's land frontier, when Gaddafi troops battled rebels on Tunisian territory for control of the Dehiba-Wazin frontier crossing. The incursion…