Add support for $pmux in btor back-end
Add support for $pmux in btor back-end

antmicro/yosys,azonenberg/yosys,YosysHQ/yosys,antmicro/yosys,azonenberg/yosys,SymbiFlow/yosys,YosysHQ/yosys,antmicro/yosys,antmicro/yosys,azonenberg/yosys,SymbiFlow/yosys,cliffordwolf/yosys,SymbiFlow/yosys,antmicro/yosys,azonenberg/yosys,cliffordwolf/yosys,azonenberg/yosys,SymbiFlow/yosys,azonenberg/yosys,YosysHQ/yosys,YosysHQ/yosys,cliffordwolf/yosys,cliffordwolf/yosys,YosysHQ/yosys,YosysHQ/yosys,cliffordwolf/yosys,SymbiFlow/yosys,cliffordwolf/yosys,antmicro/yosys,YosysHQ/yosys,azonenberg/yosys,YosysHQ/yosys,cliffordwolf/yosys,SymbiFlow/yosys,azonenberg/yosys,cliffordwolf/yosys,antmicro/yosys,SymbiFlow/yosys,SymbiFlow/yosys,antmicro/yosys,cliffordwolf/yosys,azonenberg/yosys