Fix part of #2070: Correctly handle promotion for <unary-op>(int).

This still only handles a scalar correctly, and some
vector cases need additional fixes.

Test/hlsl.singleArgIntPromo.vert

@@ -0,0 +1,16 @@
+float main(): SV_Target0
+{
+    int d = 4;
+    int2 d2 = int2(5,d);
+    float  f1 = log2(5);
+    float2 f2 = log(d2);
+    float3 f3 = log(int3(7,2,3));
+    float2 f22 = log(int2(5,d));  // This case does not work yet, due to a different bug that turns this into 2 args.
+
+    int a = 5;
+    min16float b = min16float(f16tof32(a));
+    b *= b;
+    uint c = f32tof16(b);
+
+    return f1 + f2.x + f3.z + f22.y + c;
+}