[WIP] Backward compatible and thread safe re-implementation of streamlog

Created by: rete

BEGINRELEASENOTES

• Transform prefix and base_prefix classes to simple std::function
• Set default log level to MESSAGE
• Modernized and simplified logscope class

{
  // create the scope object. Sets the logger config on creation
  logscope scope( streamlog::out, "MyTrackingProcessor", "DEBUG" ) ;
  // the scope object can be released before reaching the end of the scope
  scope.release();
  // the scope automatically releases here, settings back the old logger config
}

• Introduced logconfig hidden class to handle the global logger configuration
• Changed API for global logger initialization:

// example in main()
streamlog::logstream::global_init( &std::cout, "Marlin", "MESSAGE" ) ;

• Use thread_local to make the global logger thread safe. The global_init() function initialize the config which is shared by all thread local global loggers.

ENDRELEASENOTES

Superseeds #15