Add a NEON VMOV imm encoding to the emitter.
Support other constant VMOVs on NEON.

Float is especially useful.
vertexjit: Avoid skinning VFP switching.
Implement NEON register VMOVs.
vertexjit: Avoid the VFP more in some weight funcs.
vertexjit: Use NEON for prescale as well.

Just to keep the VFP out of the picture.
vertexjit: Use NEON loads for up to 8 weights.
vertexjit: Fix non-morph 5551 decoding.

Oops, it was just wrong before.
Add a float->GP reg, fix VDUP for I_16.
vertexjit: Avoid the remaining VFP instrs.

So now, unless there's skin+morph, it should be all-NEON, I think.