Add tests for ECP5 architecture

tests/ecp5/shifter.v

@@ -0,0 +1,22 @@
+module top    (
+out,
+clk,
+in
+);
+    output [7:0] out;
+    input signed clk, in;
+    reg signed [7:0] out = 0;
+
+    always @(posedge clk)
+	begin
+`ifndef BUG
+		out    <= out >> 1;
+		out[7] <= in;
+`else
+
+		out    <= out << 1;
+		out[7] <= in;
+`endif
+	end
+
+endmodule