Most fans have heard that “Logan,” Fox’s third spinoff movie featuring Wolverine, is supposedly Hugh Jackman’s final appearance as the most popular X-Man of all. But what about Professor X, the wheelchair-bound leader of the mutant hero group who has long been a father figure to the semi-immortal, rage-fueled slasher? That other series stalwart, Patrick Stewart, who’s played the older version of the powerful telepath in six previous movies, is the only major franchise mainstay to share the screen with Jackman in “Logan.” And much as this second R-rated, ultrabrutal X movie feels like a Wolverine send-off, Professor Xavier’s fate seems decided in it as well.