Twenty years after they permanently lowered the bar on broad and dumb character comedies, Lloyd and Harry are back, “Dumb and Dumber” than ever in “Dumb and Dumber To.” And within moments of the opening credits, you may find yourself overcome with sentimental warmth at seeing two 50something actors as characters that the years have not made smarter. Jim Carrey and Jeff Daniels energetically reprise their popular roles, and the warmth follows.