[experimental-ims] 7dd921d Add missing header for string concatention operator

[Geoff Simmons]

commit 7dd921d647dff4b9b1abdfc61346c4e3f357546f
Author: Cosimo Streppone <cosimo at streppone.it>
Date:   Thu Aug 25 09:17:22 2011 +0200

    Add missing header for string concatention operator

diff --git a/doc/sphinx/installation/upgrade.rst b/doc/sphinx/installation/upgrade.rst
index 2afbf64..5f40422 100644
--- a/doc/sphinx/installation/upgrade.rst
+++ b/doc/sphinx/installation/upgrade.rst
@@ -9,6 +9,8 @@ Changes to VCL
 
 In most cases you need to update your VCL since there has been some changes to the syntax.
 
+string concatenation operator
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 String concatenation did not have an operator previously, but this has now been changed to ``+``.
 
 ``log`` moved to the std vmod