Added hint about changing the prompt in $PYTHONSTARTUP

Doc/tut.tex

@@ -302,6 +302,8 @@ explicit source of commands (which otherwise behaves like an
 interactive session).  It is executed in the same name space where
 interactive commands are executed, so that objects that it defines or
 imports can be used without qualification in the interactive session.
+You can also change the prompts {\tt sys.ps1} and {\tt sys.ps2} in
+this file.
 
 If you want to read an additional start-up file from the current
 directory, you can program this in the global start-up file, e.g.

Doc/tut/tut.tex

@@ -302,6 +302,8 @@ explicit source of commands (which otherwise behaves like an
 interactive session).  It is executed in the same name space where
 interactive commands are executed, so that objects that it defines or
 imports can be used without qualification in the interactive session.
+You can also change the prompts {\tt sys.ps1} and {\tt sys.ps2} in
+this file.
 
 If you want to read an additional start-up file from the current
 directory, you can program this in the global start-up file, e.g.