Use merge instead of append (#7341)

.htaccess

@@ -34,8 +34,8 @@ Options -Indexes
 # Disable page indexing
 Header set X-Robots-Tag "noindex, nofollow"
 
-# replace 'append' with 'merge' for Apache version 2.2.9 and later
-#Header append Cache-Control public env=!NO_CACHE
+# replace 'merge' with 'append' for Apache < 2.2.9
+#Header merge Cache-Control public env=!NO_CACHE
 
 # Optional security headers
 # Only provides increased security if the browser supports those features

INSTALL

@@ -252,11 +252,6 @@ To enable these features in apache the following modules need to be enabled:
 The optimisation is already included in the .htaccess file in the top 
 directory of your installation.
 
-If you are using Apache version 2.2.9 and later, in the .htaccess file
-change the 'append' word to 'merge' for a more correct response. Keeping
-as 'append' shouldn't cause any problems though changing to merge will 
-eliminate the possibility of duplicate 'public' headers in Cache-control.
-
 Lighttpd:
 ---------
 With Lightty the addition of Expire: tags by mod_expire is incompatible with