PERF: Use the faster TransformPhysicalPointToIndex overload in filter

Replaced `image->TransformPhysicalPointToIndex(point, index)` call by
`image->TransformPhysicalPointToIndex(point)`, which is slightly faster,
as it does not figure out whether or not the point is inside the image.

Follow-up to pull request #993
commit 0703516
"STYLE: Use image->TransformPhysicalPointToIndex(point), returning index"

Modules/Filtering/LabelMap/include/itkShapePositionLabelMapFilter.h

@@ -117,7 +117,7 @@ class ITK_TEMPLATE_EXPORT ShapePositionLabelMapFilter : public InPlaceLabelMapFi
         point[i] = static_cast<OffsetValueType>(position[i]); // FIXME: use next line instead.
         // point[i] = static_cast<CoordinateType>( position[i] );
       }
-      this->GetOutput()->TransformPhysicalPointToIndex(point, idx);
+      idx = this->GetOutput()->TransformPhysicalPointToIndex(point);
     }
     else
     {