They took off from a desert and landed in a numbing rain with snow was in the forecast. And then, if that weren’t strange enough, they were taken to Salem. On Halloween weekend. For the 22 Libyan fighters airlifted to Logan International Airport yesterday, the first of the injured to arrive in the United States for medical treatment after the overthrow of Moammar Khadafy’s government less than two weeks ago, it was a day of great joy and great culture shock.