vertexjit: Implement Morph pos/nrm variants on x86

Not doing color for two reasons: it seems complicated, and I didn't easily find any games that use it.

Anyway, LittleBigPlanet for example uses this.  Naturally, x86 doesn't need this so much but seems like ARM could do roughly the same...

S8/S16 generate a bit of code for large morphcounts.  I considered making it a real loop (there's enough regs), but not sure if it really matters that much.

-[Unknown]