The lure of the wild has recently attracted an interesting batch of solitude seekers: Reese Witherspoon ("Wild"), Mia Wasikowska ("Tracks") and Robert Redford, twice. Two years after "All Is Lost," Redford has swapped the sea for the woods, and wordless isolation for Nick Nolte. It's not a bad trade. "A Walk in the Woods" is a broad and congenial comedy about two aged old friends trying to hike all 2,000-plus miles of the Appalachian Trail, from Georgia to Maine.