Add defvalue test, minor autotest fixes for .sv files

Signed-off-by: Clifford Wolf <clifford@clifford.at>

tests/simple/defvalue.sv

@@ -0,0 +1,22 @@
+module top(input clock, input [3:0] delta, output [3:0] cnt1, cnt2);
+	cnt #(1) foo (.clock, .cnt(cnt1), .delta);
+	cnt #(2) bar (.clock, .cnt(cnt2));
+endmodule
+
+module cnt #(
+	parameter integer initval = 0
+) (
+	input clock,
+	output logic [3:0] cnt = initval,
+`ifdef __ICARUS__
+	input [3:0] delta
+`else
+	input [3:0] delta = 10
+`endif
+);
+`ifdef __ICARUS__
+	assign (weak0, weak1) delta = 10;
+`endif
+	always @(posedge clock)
+		cnt <= cnt + delta;
+endmodule