SANTA MONICA, Calif., Feb. 17, 2000 -- Charlton Heston, call your agent. Twentieth Century Fox's long-anticipated "Planet of the Apes" remake is not extinct. And ditto for -- Warner Bros.' new-look "Superman" movie may fly after all. Word comes today from the Hollywood Reporter that these big-budget sci-fi and super-hero projects -- two of the most highly anticipated movies of the 1990s that never came to pass -- may soon be salvaged from development hell after years of on-again, off-again dire