Argentina’s president called on Britain on Thursday to relinquish control of the Falkland Islands, accusing London of taking part in an act of “blatant colonialism” in claiming the wind-swept archipelago. Cristina Fernández de Kirchner published an open letter in the Guardian newspaper urging Prime Minister David Cameron to honor U.N. resolutions which she says backs her case for the return of the islands, which Argentina calls the Malvinas. She has made several similar demands in the past. …