HLSL: Fix issue #658: Don't adopt initializer constness from declaration.

This also makes it match how GLSL handles the same thing.

Test/hlsl.init2.frag

@@ -18,6 +18,25 @@ void Test1()
 
     struct mystruct2 { float a; float b; float c; };
     mystruct2 test5 = { {8,}, {9,}, {10}, };
+    const mystruct2 constTest5 = { {8,}, {9,}, {10}, };
+    constTest5.c;
+
+    const float step = 1.f;
+    float n = 0;
+    const float3 a[8] = {
+            normalize(float3(1, 1, 1)) * (n += step),
+            normalize(float3(-1, -1, -1)) * (n += step),
+            normalize(float3(-1, -1, 1)) * (n += step),
+            normalize(float3(-1, 1, -1)) * (n += step),
+            normalize(float3(-1, 1, 1)) * (n += step),
+            normalize(float3(1, -1, -1)) * (n += step),
+            normalize(float3(1, -1, 1)) * (n += step),
+            normalize(float3(1, 1, -1)) * (n += step) };
+
+    const struct one { float3 a; } oneNonConst = { normalize(float3(-1, 1, 1)) * (n += step) };
+    const struct two { float3 a;
+                       float3 b; } twoNonConst = { normalize(float3(-1, 1, 1)) * (n += step),
+                                                   normalize(float3(-1, 1, 1)) * (n += step) };
 }
 
 struct PS_OUTPUT { float4 color : SV_Target0; };