Update help topic for Prefs Code Formatting tab

Added info about the new "Repeat comments in unit implementation
section" check box on the Code Formatting tab of the Preferences
dialogue box.

Author: delphidabbler

Src/Help/HTML/dlg_prefs_sourcecode.htm

@@ -69,6 +69,12 @@ <h2>
       comment to use just the first paragraph of the snippet's description by
       ticking the <em>Truncate comments to one paragraph</em> check box.
     </p>
+    <p>
+      When descriptive comments are enabled, they are included in the interface
+      section of generated units. You can choose whether or not such comments 
+      are repeated in the unit's implementation section using the <em>Repeat
+      comments in unit implementation section</em> check box.
+    </p>
     <p>
       <strong>Note:</strong> Descriptive comments are not applicable to
       <a href="snippet_freeform.htm">freeform</a> or