Support packed arrays in struct/union.

tests/svtypes/struct_array.sv

@@ -0,0 +1,22 @@
+// test for array indexing in structures
+
+module top;
+	
+	struct packed {
+		bit [5:0] [7:0] a;	// 6 element packed array of bytes
+		bit [15:0] b;		// filler for non-zero offset
+	} s;
+
+	initial begin
+		s = '0;
+
+		s.a[2:1] = 16'h1234;
+		s.a[5] = 8'h42;
+
+		s.b = '1;
+		s.b[1:0] = '0;
+	end
+
+	always_comb assert(s==64'h4200_0012_3400_FFFC);
+
+endmodule