It was a simpler time. Sinew, firepower and muscle mass would save the day, whatever day needed saving. Forget “Iron Man” or “Captain Marvel”: heroes could be identified by their first names – Sly, Arnie, Bruce – regardless of what roles they took. In the 1980s and ’90s, these men and their rivals pummelled their way through legions of wrong ’uns with whatever arsenal came to hand.  As the story goes, and is retold in Nick de Semlyen’s new book, The Last Action Heroes, Arnold Schwarzenegger had a lifelong dream of cutting off somebody’s arm on screen then using it as an assault weapon. The fantasy was denied him in his famously profligate 1985 shoot-’em-up Commando, but we’re told he’ll get to do it in this autumn’s forthcoming action-comedy Kung Fury 2, in which he plays none other than the US President. The Last Action Heroes is a romp through the heyday of the action movie – the pre-CGI, pre-Marvel heyday, that is, which stands tall as a kind of Golden Age for the trashy purity of the form.…