Anyone who has visited the IFC Center in winter knows the particular pain of waiting in line for a popular film in the freezing cold. No, it’s not an effort to separate the diehard arthouse film enthusiasts from the weak dilettantes. The center, formerly the Waverly Theater and before that a church, is just really old and the owners sacrificed lobby space for screens. But now, relief for those long lines– and much more– may be on the way. The IFC Center is preparing for a serious upgrade, with plans to double the size of its building and add six new screens.