It was decided that the performance benefits that isolates offer (faster spin-up times for worker processes, faster inter-worker communication, possibly a lower memory footprint) are not actual bottlenecks for most people and do not outweigh the potential stability issues and intrusive changes to the code base that first-class support for isolates requires. Hence, this commit backs out all isolates-related changes. Good bye, isolates. We hardly knew ye.
node::Loop() replaces the NODE_LOOP macro. This avoids hitting v8::Isolate::GetCurrent() for each loop lookup when HAVE_ISOLATE==0