We have forgotten how subtle Al Pacino could be, pre “Hoo Hah!” Something about his Oscar winning turn in “Scent of a Woman” unleashed the beast, a performer as big, broad and puffed up as that mountain of hair he keeps teased about his head. So it’s a bit of a jolt to see him as Simon Axler, a famous, fading stage and screen actor who is losing his grip and ability to stay on script in “The Humbling.”