Set up inlining infrastructure
Introduce ToX4, ToX4TypedObject MIR and SIMDInputsPolicy
Introduce SIMD LIRs
Allocate SIMD Registers
Implement SIMD codegen for x86 and x64
Picked up Niko's CreateZeroedSIMDWrapper
Generate machine instructions for ToX4 and ToX4TypedObject
Introduce fpreg_value_t