HLSL: allow multi-dimensional arrays

All the underpinnings are there; this just parses multiple array dimensions
and passes them through to the existing mechanisms.

Also, minor comment fixes, and add a new test for multi-dim arrays.

Test/hlsl.array.multidim.frag

@@ -0,0 +1,20 @@
+
+float float_array[5][4][3];
+
+struct PS_OUTPUT
+{
+    float4 Color : SV_Target0;
+};
+
+PS_OUTPUT main()
+{
+    float4 float4_array_1[2][3];
+    float4 float4_array_2[5][3];
+
+    float4_array_1[1][2] = float_array[2][3][1];
+    float4_array_2[1] = float4_array_1[0];
+
+    PS_OUTPUT psout;
+    psout.Color = float4_array_1[1][2];
+    return psout;
+}