major array pack and flatten update (closes #48)

- dimensions flattening conversion only flattens packed dimensions
- conversion for packing arrays when necessary (preserves memories)
- added coverage for array with multiple packed dimensions
- test runner no longer forbids multi-dim accesses after conversion
- Decl and subordinate types derive Ord

test/basic/packed_array.v

@@ -0,0 +1,15 @@
+module top;
+    reg arr [1:0][2:0][3:0];
+    initial begin : block_name
+        integer i, j, k;
+        for (i = 0; i <= 1; i++) begin
+            for (j = 0; j <= 2; j++) begin
+                for (k = 0; k <= 3; k++) begin
+                    $display("%b", arr[i][j][k]);
+                    arr[i][j][k] = i+j+k;
+                    $display("%b", arr[i][j][k]);
+                end
+            end
+        end
+    end
+endmodule