Philadelphia Daily News: AS THAT great philosopher Kermit the Frog once said, it’s not easy being green. And it’s not going to seem any simpler after tonight’s two-hour “Frontline” presentation, “Heat,” in which correspondent Martin Smith takes viewers on a tour of the roadblocks that currently stand between 6.5 billion Earthlings and any serious attempts to halt global warming. But first there’s a detour to Mount Everest, where mountain climber and filmmaker David Breashears leaves Smith behind for an …