SPV 1.4: Lookup tables: Use variable initializer and NonWritable...

...when doing a variable lookup on an array of constants.

Test/spv.1.4.NonWritable.frag

@@ -0,0 +1,13 @@
+#version 450
+
+layout(location = 0) flat in int index;
+
+layout(location = 0) out float color;
+
+// lookup table
+const float table[16] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
+
+void main()
+{
+    color = table[index];
+}