squeak: add enumeration prims, make GC safe to use during enumeration
squeak: add enumeration prims, make GC safe to use during enumeration

LivelyKernel/LivelyKernel,NikolaySuslov/LivelyKernel,NikolaySuslov/LivelyKernel,pascience/LivelyKernel,pascience/LivelyKernel,LivelyKernel/LivelyKernel,NikolaySuslov/LivelyKernel,pascience/LivelyKernel,LivelyKernel/LivelyKernel