COMP: Use C++ headers over C header

Some headers from C library were deprecated in C++ and are no longer
welcome in C++ codebases. Some have no effect in C++. For more details
refer to the C++ 14 Standard [depr.c.headers] section.

This patch replaces C standard library headers with their C++
alternatives and removes redundant ones.

test/itkIteratorTests.cxx

@@ -21,7 +21,7 @@
 #include "itkImage.h"
 #include "itkVector.h"
 #include "itkRLEImage.h"
-#include <time.h>
+#include <ctime>
 
 int itkIteratorTests(int, char* [] )
 {