Congolese artists are helping President Joseph Mobutu rewrite history these days, painting huge canvases that show the grim, young president peering steadfastly ahead with a ghostly Patrice Lumumba at his side. It is all part of a campaign that depicts Mobutu as a great militant African nationalist, the apostle and heir of Lumumba, and as the great enemy of imperialism, neocolonialism, mercenaries, and Moise Tshombe. To maintain this pose requires some glib talk and some artful dodging of facts. Mobutu, a 36-year old former newspaperman, has been successful at both. So successful, in fact, that African leaders at the recent summit conference of the Organization of African Unity here put aside the past and hailed Mobutu for all he claimed to be. In the long run, the Congo may gain from Mobutu's rewriting of the past, but, for the sake of the record, it is worthwhile comparing the claims of the new Mobutu with the facts about the old Mobutu and the histories of Lumumba, Tshombe and the mercenaries...