Rename ErrorCallback into LogSystem, provide a proper console API

include/AdblockPlus/LogSystem.h

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2013 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 ADBLOCK_PLUS_ERROR_CALLBACK_H
-#define ADBLOCK_PLUS_ERROR_CALLBACK_H
+#ifndef ADBLOCK_PLUS_LOG_SYSTEM_H
+#define ADBLOCK_PLUS_LOG_SYSTEM_H
 
 #include <string>
 
 #include "tr1_memory.h"
 
 namespace AdblockPlus
 {
-  class ErrorCallback
+  class LogSystem
   {
   public:
-    virtual ~ErrorCallback();
-    virtual void operator()(const std::string& message) = 0;
+    enum LogLevel {TRACE, LOG, INFO, WARN, ERROR};

[Felix Dahlke, 2013/05/13 07:20:15]

The common approach is to prefix enum values with the enum name, e.g.:
LOG_LEVEL_TRACE. Oleksandr has already changes this as it didn't compile on
Windows.

+
+    virtual ~LogSystem() {}
+    virtual void operator()(LogLevel logLevel, const std::string& message,
+          const std::string& source) = 0;
   };
 
-  typedef std::tr1::shared_ptr<ErrorCallback> ErrorCallbackPtr;
+  typedef std::tr1::shared_ptr<LogSystem> LogSystemPtr;
 }
 
 #endif