Issue 5013 - Make parameter const ref when applicable.

src/Thread.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #ifndef ADBLOCKPLUS_THREAD_H
 #define ADBLOCKPLUS_THREAD_H
 
 #ifdef WIN32
 #include <windows.h>
 #else
 #include <pthread.h>
 #endif
 
 namespace AdblockPlus
 {
-  void Sleep(const int millis);
+  void Sleep(int millis);
 
   class Mutex
   {
   public:
 #ifdef WIN32
     CRITICAL_SECTION nativeMutex;
 #else
     pthread_mutex_t nativeMutex;
 #endif
 
@@ skipping 27 matching lines @@
 #ifdef WIN32
     HANDLE nativeThread;
 #else
     pthread_t nativeThread;
 #endif
     bool m_deleteSelfOnFinish;
   };
 }
 
 #endif