Merge branch '3.4' into 4.4

* 3.4:
  Change code example for custom header when using a reverse proxy

Author: javiereguiluz

deployment/proxies.rst

@@ -111,7 +111,7 @@ In this case, you'll need to set the header ``X-Forwarded-Proto`` with the value
     // public/index.php
 
     // ...
-    $_SERVER['HEADER_X_FORWARDED_PROTO'] = $_SERVER['HEADER_CUSTOM_FORWARDED_PROTO'];
+    $_SERVER['HTTP_X_FORWARDED_PROTO'] = $_SERVER['HTTP_CUSTOM_FORWARDED_PROTO'];
     // ...
     $response = $kernel->handle($request);