Shifters and Extenders
	new file:   Shifter.sym
	new file:   Shifter.v
	new file:   Shifter_tb.v
	new file:   sign_extend4_16.sym
	new file:   sign_extend4_16.v
	new file:   sign_extend8_16.sym
	new file:   sign_extend_16_tb.v
	new file:   sign_extend_tb.v