When Oliver Stone’s Vietnam War drama “Platoon,” premiered in December 1986, the cast was concerned it wouldn’t do well. Massive military blockbusters like “Top Gun” had captured movie-goers attention, and for the actors who worked for 54 days in the sweltering heat in the Philippines on “Platoon,” it seemed like the film might go unnoticed. Or worse, the gritty war epic might get mistaken for a bland action movie that only took place in Vietnam, rather than a film about what it felt like to serve there.