BUG: Replace Math::Round with std::round for double-to-double rounding

According to https://github.com/InsightSoftwareConsortium/ITK/blob/66ab5b14c476d057ed46a4daba05b710681160e6/Modules/Core/Common/include/itkMath.h#L127 the `TReturn` template argument of `Math::Round` must be an integer type. For double-to-double rounding, a call to `std::round` is preferred.

Core/ComponentBaseClasses/elxOptimizerBase.hxx

@@ -23,6 +23,7 @@
 
 #include "itkSingleValuedNonLinearOptimizer.h"
 #include "itk_zlib.h"
+#include <cmath> // For round.
 
 namespace elastix
 {
@@ -83,7 +84,7 @@ OptimizerBase<TElastix>::AfterRegistrationBase()
   ParametersType      roundedTP(N);
   for (unsigned int i = 0; i < N; ++i)
   {
-    roundedTP[i] = itk::Math::Round<ParametersValueType>(finalTP[i] * 1.0e6);
+    roundedTP[i] = std::round(finalTP[i] * 1.0e6);
   }
 
   /** Compute the crc checksum using zlib crc32 function. */