pthread_barrier.h - update licence comment
pthread_barrier.h - update licence comment

Use correct open source licence verbage as per today's email from
Brent Priddy (toopriddy@gmail.com) to Ken McDonell.

adfernandes/pcp,andyvand/cygpcpfans,aeg-aeg/pcpfans,prasincs/pcp,mbaldessari/pcp,tjanez/pcp,prasincs/pcp,edwardt/pcp,tjanez/pcp,edwardt/pcp,edwardt/pcp,mbaldessari/pcp,wuliming/pcp,ryandoyle/pcp_original,aeg-aeg/pcpfans,prasincs/pcp,ryandoyle/pcp_original,wuliming/pcp,aeg-aeg/pcpfans,andyvand/cygpcpfans,andyvand/cygpcpfans,andyvand/cygpcpfans,mbaldessari/pcp,andyvand/cygpcpfans,andyvand/cygpcpfans,tjanez/pcp,wuliming/pcp,wuliming/pcp,andyvand/cygpcpfans,aeg-aeg/pcpfans,adfernandes/pcp,ryandoyle/pcp_original,edwardt/pcp,adfernandes/pcp,wuliming/pcp,aeg-aeg/pcpfans,edwardt/pcp,aeg-aeg/pcpfans,wuliming/pcp,adfernandes/pcp,tjanez/pcp,tjanez/pcp,adfernandes/pcp,edwardt/pcp,tjanez/pcp,ryandoyle/pcp_original,prasincs/pcp,prasincs/pcp,ryandoyle/pcp_original,mbaldessari/pcp,adfernandes/pcp,mbaldessari/pcp,prasincs/pcp,ryandoyle/pcp_original,prasincs/pcp,edwardt/pcp,aeg-aeg/pcpfans,andyvand/cygpcpfans,tjanez/pcp,ryandoyle/pcp_original,wuliming/pcp,edwardt/pcp,prasincs/pcp,wuliming/pcp,adfernandes/pcp,mbaldessari/pcp,tjanez/pcp,aeg-aeg/pcpfans,ryandoyle/pcp_original,adfernandes/pcp