vertexjit: Optimize u8/u16 weights a little.

Only for uncommon values.
vertexjit: Initial u8/u16 weights for d3d9.
Oops, forgot to multiply.
vertexjit: Optimize the d3d9 weights a bit.

Only used without skinning on, or with morph, of course.
Fix DX9 bbox crash (DrawEngine::decoded wasn't initialized, because it also existed in the DX9 draw engine)
Move GetCurrentSimpleVertices to DrawEngineCommon
Clean up some indentation
D3D: Specify maxindex correctly in DrawIndexedPrimitive
DX9: Specify max index correctly
Really set maxindex correctly..
Reduce the diff between the two draw engines
More code deduplication. Also normalized some line endings.
vertexjit: Use SSE for all weights, u8/u16.
vertexjit: Use SSE4 in tc u8/u16 code.

It's not much different for non-SSE 4, might as well be common.
Merge pull request #6917 from unknownbrackets/vertexjit

Add x86 weight ToFloat handling for d3d9