COMP: include stdlib.h for SWIG free/malloc with the Stable ABI

Needed by SWIG for free/malloc, but not included by Python.h with recent versions of the Stable ABI

Addresses:

  C:\P\IPP\ITK-win_311-x64\Wrapping\Modules\ITKIOImageBase\itkImageSeriesWriterPython.cpp(1416): error C3861: 'free': identifier not found
  C:\P\IPP\ITK-win_311-x64\Wrapping\Modules\ITKIOImageBase\itkImageSeriesWriterPython.cpp(1562): error C3861: 'malloc': identifier not found

Wrapping/Generators/Python/PyBase/pyBase.i

@@ -11,6 +11,11 @@ if _version_info < (3, 7, 0):
 from . import _ITKCommonPython
 %}
 
+%{
+// Needed by SWIG for free/malloc, but not included by Python.h with recent versions of the Stable ABI
+#include "stdlib.h"
+%}
+
 //By including pyabc.i and using the -py3 command line option when calling SWIG,
 //the proxy classes of the STL containers will automatically gain an appropriate
 //abstract base class.