STYLE: Remove & from LinearInterpolateImageFunction distance variables

There appear no need to avoid copying expressions like

    index[i] - static_cast<InternalComputationType>(basei[i])

So it appears unnecessary to bind such expression to a reference. It's simpler
to just copy such an expression.

Modules/Core/ImageFunction/include/itkLinearInterpolateImageFunction.h

@@ -135,7 +135,7 @@ class ITK_TEMPLATE_EXPORT LinearInterpolateImageFunction : public InterpolateIma
     IndexType basei;
     basei[0] = std::max(Math::Floor<IndexValueType>(index[0]), this->m_StartIndex[0]);
 
-    const InternalComputationType & distance = index[0] - static_cast<InternalComputationType>(basei[0]);
+    const InternalComputationType distance = index[0] - static_cast<InternalComputationType>(basei[0]);
 
     const TInputImage * const inputImagePtr = this->GetInputImage();
     const RealType &          val0 = inputImagePtr->GetPixel(basei);
@@ -160,10 +160,10 @@ class ITK_TEMPLATE_EXPORT LinearInterpolateImageFunction : public InterpolateIma
     IndexType basei;
 
     basei[0] = std::max(Math::Floor<IndexValueType>(index[0]), this->m_StartIndex[0]);
-    const InternalComputationType & distance0 = index[0] - static_cast<InternalComputationType>(basei[0]);
+    const InternalComputationType distance0 = index[0] - static_cast<InternalComputationType>(basei[0]);
 
     basei[1] = std::max(Math::Floor<IndexValueType>(index[1]), this->m_StartIndex[1]);
-    const InternalComputationType & distance1 = index[1] - static_cast<InternalComputationType>(basei[1]);
+    const InternalComputationType distance1 = index[1] - static_cast<InternalComputationType>(basei[1]);
 
     const TInputImage * const inputImagePtr = this->GetInputImage();
     const RealType &          val00 = inputImagePtr->GetPixel(basei);
@@ -228,13 +228,13 @@ class ITK_TEMPLATE_EXPORT LinearInterpolateImageFunction : public InterpolateIma
   {
     IndexType basei;
     basei[0] = std::max(Math::Floor<IndexValueType>(index[0]), this->m_StartIndex[0]);
-    const InternalComputationType & distance0 = index[0] - static_cast<InternalComputationType>(basei[0]);
+    const InternalComputationType distance0 = index[0] - static_cast<InternalComputationType>(basei[0]);
 
     basei[1] = std::max(Math::Floor<IndexValueType>(index[1]), this->m_StartIndex[1]);
-    const InternalComputationType & distance1 = index[1] - static_cast<InternalComputationType>(basei[1]);
+    const InternalComputationType distance1 = index[1] - static_cast<InternalComputationType>(basei[1]);
 
     basei[2] = std::max(Math::Floor<IndexValueType>(index[2]), this->m_StartIndex[2]);
-    const InternalComputationType & distance2 = index[2] - static_cast<InternalComputationType>(basei[2]);
+    const InternalComputationType distance2 = index[2] - static_cast<InternalComputationType>(basei[2]);
 
     const TInputImage * const inputImagePtr = this->GetInputImage();
     const RealType &          val000 = inputImagePtr->GetPixel(basei);