Is it just global warming, or has it gotten a tad steamy in the multiplex lately? No sooner had viewers taken in the long, graphic lesbian sex scenes in the French coming-of-age drama “Blue Is the Warmest Color” last year than they were treated to “Stranger by the Lake,” a homoerotic thriller (also French) set in a gay cruising site, at which men could be seen pleasuring each other and themselves with unsettling, frankness. ........................................................ The challenge today is that, rather than being relegated to disreputable theaters or scruffy back sections of video stores, porn is on the home entertainment...