Add SWIG_PYTHON_NO_DEBUG macro for building Debug wrappers against the Python Debug dll

Doc/Manual/Python.html

@@ -795,7 +795,9 @@ If you need to build it on your own, the following notes are provided:
 You will need to create a DLL that can be loaded into the interpreter. 
 This section briefly describes the use of SWIG with Microsoft Visual
 C++.   As a starting point, many of SWIG's examples include project
-files.  You might want to take a quick look at these in addition to
+files (.dsp files) for Visual C++ 6. These can be opened by more 
+recent versions of Visual Studio.
+You might want to take a quick look at these examples in addition to
 reading this section.
 </p>
 
@@ -868,6 +870,24 @@ set of Win32 debug or thread libraries.  You will have to fiddle around with
 the build options of project to try and track this down.
 </p>
 
+<p>
+A 'Debug' build of the wrappers requires a debug build of the Python interpreter.
+This normally requires building the Python interpreter from source, which is not a
+job for the feint-hearted. Alternatively you can use the 'Release' build of the
+Python interpreter with a 'Debug' build of your wrappers by defining the <tt>SWIG_PYTHON_NO_DEBUG</tt>
+symbol under the preprocessor options. Or you can ensure this macro is defined at the beginning
+of the wrapper code using the following in your interface file, where <tt>_MSC_VER</tt> ensures it is
+only used by the Visual Studio compiler:
+</p>
+
+<div class="code"><pre>
+%begin %{
+#ifdef _MSC_VER
+#define SWIG_PYTHON_NO_DEBUG
+#endif
+%}
+</pre></div>
+
 <p>
 Some users have reported success in building extension modules using Cygwin
 and other compilers.  However, the problem of building usable DLLs with these