Over the last three-plus decades, filmmaker Richard Linklater has made 20 movies covering a number of genres, a few of which he likes to revisit. The most notable of these is the “Before” franchise, starring Ethan Hawke and Julie Delpy, which follows a couple over the space of almost two decades wherein they meet, get hitched, break up, and find a tolerable middle ground as friends. Linklater’s breakout feature stoner-comedy “Dazed and Confused” (1993) found a bookend in 2016 with “Everybody Wants Some!!” Linklater was nominated for multiple Oscars for “Boyhood” (also featuring Hawke), a film that took a dozen years to shoot, mostly because he wanted to present the performers aging naturally. He’s doing this again with his next project “Merrily We Roll Along,” the second film adaptation of the musical stage play by Stephen Sondheim and George Furth. Linklater will spend 20 years on that production. This is a …