update MS4W url

Author: jmckenna

en/optimization/debugging.txt

@@ -379,7 +379,7 @@ Using map2img
 The recommended way to test your mapfile is to use the MapServer
 commandline utility :ref:`map2img`, to verify that your mapfile
 creates a valid map image. :ref:`map2img` should be included in your
-MapServer installation (`MS4W <https://ms4w.com_ users
+MapServer installation (`MS4W <https://ms4w.com>`__ users
 need to execute *setenv.bat* before using the utility).
 
 You can set the *DEBUG* level by passing the :ref:`map2img` following
@@ -548,7 +548,7 @@ Windows users will usually find Apache's log files in a path similar to:
 
   C:\Program Files\Apache Group\Apache2\logs
 
-MapServer for Windows (`MS4W <https://ms4w.com_) users
+MapServer for Windows (`MS4W <https://ms4w.com>`__) users
 will find Apache's log files at:
 
 ::