Ported r2628 from ZXing
Ported r2628 from ZXing

Original commit message: "const-ness and iphone/objc fixes"

Kalvar/ZXingObjC,cortices/ZXingObjC,peacemoon/ZXingObjC,tejesh-alimilli/ZXingObjC,Stocard/ZXingObjC,ufs-slizhik/ZXingObjC,elegion/ios-pods-ZXingObjC,TheLevelUp/ZXingObjC,JeremyPacker/ZXingObjC,fanwenkai/ZXingObjC,trsathya/ZXingObjC,xuxubin/ZXingObjC,davidjackman/ZXingObjC,benjohnde/ZXingObjC,Kevin775263419/ZXingObjC,Kalvar/ZXingObjC,TheLevelUp/ZXingObjC,Kevin775263419/ZXingObjC,jebai0521/ZXingObjC,Stocard/ZXingObjC,adan016/ZXingObjC,fuzhiqiang1989/ZXingObjC,zeffon/ZXingObjC,zilaiyedaren/ZXingObjC,benjohnde/ZXingObjC,fanwenkai/ZXingObjC,peacemoon/ZXingObjC,wuxsoft/ZXingObjC,zilaiyedaren/ZXingObjC,YotrolZ/ZXingObjC,sdhzwm/ZXingObjC,sdhzwm/ZXingObjC,xuxubin/ZXingObjC,rowliny/ZXingObjC,rowliny/ZXingObjC,davidjackman/ZXingObjC,adan016/ZXingObjC,fuzhiqiang1989/ZXingObjC,elegion/ios-pods-ZXingObjC,YotrolZ/ZXingObjC,RockyAo/ZXingObjC,ufs-slizhik/ZXingObjC,cortices/ZXingObjC,tejesh-alimilli/ZXingObjC,RockyAo/ZXingObjC,trsathya/ZXingObjC,jianwoo/ZXingObjC,jianwoo/ZXingObjC,wuxsoft/ZXingObjC,zeffon/ZXingObjC,jebai0521/ZXingObjC,rkpant/ZXingObjC,rkpant/ZXingObjC,JeremyPacker/ZXingObjC