fix signed/unsigned comparison in buffer access code
fix signed/unsigned comparison in buffer access code

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