make posix.unistd more const-correct
make posix.unistd more const-correct

roxyboy/cython,mrGeen/cython,mrGeen/cython,slonik-az/cython,acrispin/cython,hickford/cython,ABcDexter/cython,andreasvc/cython,JelleZijlstra/cython,da-woods/cython,hickford/cython,marscher/cython,fabianrost84/cython,cython/cython,achernet/cython,acrispin/cython,encukou/cython,ChristopherHogan/cython,madjar/cython,da-woods/cython,achernet/cython,dahebolangkuan/cython,encukou/cython,hhsprings/cython,madjar/cython,roxyboy/cython,slonik-az/cython,mcanthony/cython,fabianrost84/cython,andreasvc/cython,dahebolangkuan/cython,mrGeen/cython,scoder/cython,mrGeen/cython,fperez/cython,encukou/cython,c-blake/cython,ABcDexter/cython,fperez/cython,encukou/cython,hickford/cython,andreasvc/cython,madjar/cython,JelleZijlstra/cython,ABcDexter/cython,scoder/cython,andreasvc/cython,ABcDexter/cython,c-blake/cython,mcanthony/cython,slonik-az/cython,c-blake/cython,mcanthony/cython,hhsprings/cython,hickford/cython,c-blake/cython,ChristopherHogan/cython,mcanthony/cython,acrispin/cython,dahebolangkuan/cython,roxyboy/cython,dahebolangkuan/cython,hhsprings/cython,achernet/cython,fperez/cython,roxyboy/cython,marscher/cython,hickford/cython,da-woods/cython,madjar/cython,acrispin/cython,mrGeen/cython,marscher/cython,achernet/cython,acrispin/cython,marscher/cython,roxyboy/cython,c-blake/cython,cython/cython,dahebolangkuan/cython,marscher/cython,fperez/cython,andreasvc/cython,JelleZijlstra/cython,hhsprings/cython,cython/cython,ChristopherHogan/cython,JelleZijlstra/cython,hhsprings/cython,fabianrost84/cython,fperez/cython,scoder/cython,madjar/cython,slonik-az/cython,scoder/cython,mcanthony/cython,cython/cython,da-woods/cython,achernet/cython,fabianrost84/cython,ABcDexter/cython,JelleZijlstra/cython,slonik-az/cython,encukou/cython,fabianrost84/cython