Changes

#Eliminate PC update. In an inline-threaded interpreter, we don't need to update the PC, because EIP encodes that. To enable this, we have to make sure no ops snoop the PC. We also need to help the GC/decompiler by making sure we have some way to provide them a PC (using a mapping or something) on demand.

#Eliminate SP update. Inside basic blocks of JSOPs, we shouldn't need to keep a proper stack. Instead, we can teach the compiler to track which logical stack element is in which register and generate faster code.

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