verilog_parser: turn S/R and R/R conflicts into hard errors.
verilog_parser: turn S/R and R/R conflicts into hard errors.

Fixes #2253.

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