formatted by Eclipse CDT
wrong copyright lines are removed because this code is too far from original example code
DifsWifiMacHelper was introduced in wifi-multihop-test.cc
header only version of DifsWifiMac and DifsWifiMacHelper
wifi-multihop-test directory
code definitions are separated to difs-wifi-mac.cc from its header file.
namespace abe was introduced
attribute Aifsn was added to abe::DifsWifiMac
Attributes cwmin and cwmax were added to abe::DifsWifiMac
cares attributes by abe::DifsWifiMacHelper