Remove useless pass-by-reference

plugins/managesieve/lib/Roundcube/rcube_sieve.php

@@ -476,7 +476,7 @@ class rcube_sieve
     /**
      * This is our own debug handler for connection
      */
-    public function debug_handler(&$sieve, $message)
+    public function debug_handler($sieve, $message)
     {
         rcube::write_log('sieve', preg_replace('/\r\n$/', '', $message));
     }

program/lib/Roundcube/rcube_imap.php

@@ -4564,7 +4564,7 @@ class rcube_imap extends rcube_storage
     /**
      * This is our own debug handler for the IMAP connection
      */
-    public function debug_handler(&$imap, $message)
+    public function debug_handler($imap, $message)
     {
         rcube::write_log('imap', $message);
     }

program/lib/Roundcube/rcube_imap_generic.php

@@ -4093,7 +4093,7 @@ class rcube_imap_generic
         }
 
         if ($this->debug_handler) {
-            call_user_func_array($this->debug_handler, array(&$this, $message));
+            call_user_func_array($this->debug_handler, array($this, $message));
         }
         else {
             echo "DEBUG: $message\n";

program/lib/Roundcube/rcube_smtp.php

@@ -377,7 +377,7 @@ class rcube_smtp
     /**
      * This is our own debug handler for the SMTP connection
      */
-    public function debug_handler(&$smtp, $message)
+    public function debug_handler($smtp, $message)
     {
         // catch AUTH commands and set anonymization flag for subsequent sends
         if (preg_match('/^Send: AUTH ([A-Z]+)/', $message, $m)) {