old_contents: from _external import *
  from boost import *
  from boost_system import *
  
  boost_thread = LibWithHeaderChecker(
  	'boost_thread',
  	'boost/thread.hpp',
  	'c++',
  	name='boost_thread',
  	dependencies=[boost, boost_system]
  	)
  
  
new_contents: from _external import *
  from boost import *
  from boost_system import *
  
  boost_thread = LibWithHeaderChecker(
  	'boost_thread',
  	'boost/thread.hpp',
  	'c++',
  	dependencies=[boost, boost_system]
  	)
  
  
subject: remove duplicated info