interface and instance array support

- support for interface instance arrays
- support for interface-using module instance arrays
- support for modport array bindings
- fix modport bindings shadowed in nested instances

test/basic/interface_array_multi.v

@@ -0,0 +1,11 @@
+module top;
+    generate
+        if (1) begin : block
+            wire [3:2][8:5] xs;
+            genvar x, y;
+            for (x = 2; x <= 3; x = x + 1)
+                for (y = 5; y <= 8; y = y + 1)
+                    assign xs[x][y] = 1'b1;
+        end
+    endgenerate
+endmodule