Add a regression test to check enum elaboration order

Test that enums are elaborated in declaration order and a enum declaration
can reference a item of an enum that was declared before it.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

ivtest/ivltests/enum_order.v

@@ -0,0 +1,25 @@
+// Verify that enums can reference items from enums declared before them
+
+module test;
+
+enum logic {
+  A = 1
+} a;
+
+enum logic {
+  B = A
+} b;
+
+enum logic {
+  C = B
+} c;
+
+initial begin
+  if (A == B && A == C) begin
+    $display("PASSED");
+  end else begin
+    $display("FAILED");
+  end
+end
+
+endmodule

ivtest/regress-sv.list

@@ -237,6 +237,7 @@ enum_in_struct		normal,-g2005-sv	ivltests
 enum_in_class		normal,-g2005-sv	ivltests
 enum_in_class_name_coll	CE,-g2005-sv		ivltests
 enum_next		normal,-g2005-sv	ivltests
+enum_order		normal,-g2005-sv	ivltests
 enum_ports		normal,-g2005-sv	ivltests
 enum_test1		normal,-g2005-sv	ivltests
 enum_test2		normal,-g2005-sv	ivltests