Fix for #795649: explain how to use TextEdit for editing Python code.

Doc/mac/using.tex

@@ -240,7 +240,9 @@ with extra features.
 
 You can create a text file with any word processing program such as
 \program{MSWord} or \program{AppleWorks} but you need to make sure
-that the file is saved as ``\ASCII'' or ``plain text''.
+that the file is saved as ``\ASCII'' or ``plain text''. This also
+works for \program{TextEdit}, but you need to use the command ``Make Plain Text``
+in the ``Format`` menu before trying to save.
 
 
 \subsubsection{Editors with Python modes}