Update documentation.

The documentation now contains the default for
vtkDelimitedTextReader::HaveHeaders (false).

Change-Id: Ie97f17d427d92243e710a0d6b85d8f6ffc67a6ea

IO/Infovis/vtkDelimitedTextReader.h

@@ -158,6 +158,7 @@ public:
 
   // Description:
   // Set/get whether to treat the first line of the file as headers.
+  // The default is false (no headers).
   vtkGetMacro(HaveHeaders, bool);
   vtkSetMacro(HaveHeaders, bool);