HDRenderLoop: Fix few warning

Assets/ScriptableRenderLoop/ShaderLibrary/Common.hlsl

                                 0.0, 0.0, 1.0, 0.0,
                                 0.0, 0.0, 0.0, 1.0 };
 
+// Using pow often result to a warning like this
+// "pow(f, e) will not work for negative f, use abs(f) or conditionally handle negative values if you expect them"
+// PositivePow remove this warning when you know the value is positive and avoid inf/NAN.
+float PositivePow(float base, float power)
+{
+    return pow(max(abs(base), float(FLT_EPSILON)), power);
+}
+
+float2 PositivePow(float2 base, float2 power)
+{
+    return pow(max(abs(base), float2(FLT_EPSILON, FLT_EPSILON)), power);
+}
+
+float3 PositivePow(float3 base, float3 power)
+{
+    return pow(max(abs(base), float3(FLT_EPSILON, FLT_EPSILON, FLT_EPSILON)), power);
+}
+
+float4 PositivePow(float4 base, float4 power)
+{
+    return pow(max(abs(base), float4(FLT_EPSILON, FLT_EPSILON, FLT_EPSILON, FLT_EPSILON)), power);
+}
+
 // ----------------------------------------------------------------------------
 // World position reconstruction / transformation
 // ----------------------------------------------------------------------------

Assets/ScriptableRenderLoop/ShaderLibrary/CommonMaterial.hlsl

     return blendWeights;
 }
 
+float LerpWhiteTo(float b, float t)
+{
+    float oneMinusT = 1.0 - t;
+    return oneMinusT + b * t;
+}
+
 float3 LerpWhiteTo(float3 b, float t)
 {
     float oneMinusT = 1.0 - t;

Assets/ScriptableRenderLoop/fptl/FptlLighting.cs

                 var bnds = rl.bounds;
                 var boxOffset = rl.center;                  // reflection volume offset relative to cube map capture point
                 var blendDistance = rl.blendDistance;
-                float imp = rl.importance;
-                //Matrix4x4 mat = rl.transform.localToWorldMatrix;
-                Vector3 cubeCapturePos = mat.GetColumn(3);      // cube map capture position in world space
-
 
                 // implicit in CalculateHDRDecodeValues() --> float ints = rl.intensity;
                 var boxProj = (rl.boxProjection != 0);
                 //Vector3 C = bnds.center;        // P + boxOffset;
                 var C = mat.MultiplyPoint(boxOffset);       // same as commented out line above when rot is identity
 
-                //Vector3 posForShaderParam = bnds.center - boxOffset;    // gives same as rl.GetComponent<Transform>().position;
-                var posForShaderParam = cubeCapturePos;        // same as commented out line above when rot is identity
                 var combinedExtent = e + new Vector3(blendDistance, blendDistance, blendDistance);
 
                 Vector3 vx = mat.GetColumn(0);