Rooney Mara, Elle Fanning, Melissa McCarthy and Shailene Woodley also up for Breakthrough Performance on Sunday. By Kara Warner Liam Hemsworth Photo: Gary Gershoff/ WireImage How do you know you’ve made it as an actor in Hollywood? When you land an MTV Movie Awards nomination in the buzzworthy Breakthrough Performance category! In the past, the award has gone to such illustrious and soon-to-be superstars like Alicia Silverstone in 1994 for “The Crush,” George Clooney in 1996 for “From Dusk till Dawn,” Matthew McConaughey in 1997 for “A Time to Kill” and, more recently, Robert Pattinson in 2009 for “Twilight” and Chlo