Bug 1051822 - Create global helper thread state on JS_Init() r=terrence

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extra : rebase_source : 2b9cd42a1011396d6c5043d86d3d5f2ad618c884
Bug 1109922 - Fix rooting issue creating Intl object r=terrence
Bug 1109913 - Don't sweep background things if no collecting zones remain r=terrence