Bug 918223 - make sure to save persdict.dat, r=ehsan

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extra : rebase_source : baffbf457b4eb9a1874ddfdda7dce1763a713a30
Bug 918031 - SpiderMonkey: Delete no-op branches. r=sstangl
Bug 918031 - IonMonkey: Make the lowering for neg more consistent across the types. r=sstangl
Bug 918031 - IonMonkey: Use useRegisterAtStart for LUnbox and LUnboxDouble on x64. r=sstangl
Bug 918031 - SpiderMonkey: Simplify trivial effective address computations to simple moves. r=sstangl