Make logger threadsafe.

src/common/Logger.cxx

@@ -51,6 +51,8 @@ void Logger::debug(const string& message)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void Logger::logMessage(const string& message, Level level)
 {
+  std::lock_guard<std::mutex> lock(mutex);
+
   if(level == Logger::Level::ERR)
   {
     cout << message << endl << std::flush;

src/common/Logger.hxx

@@ -19,6 +19,7 @@
 #define LOGGER_HXX
 
 #include <functional>
+#include <mutex>
 
 #include "bspf.hxx"
 
@@ -62,6 +63,8 @@ class Logger {
     // The list of log messages
     string myLogMessages;
 
+    std::mutex mutex;
+
   private:
     void logMessage(const string& message, Level level);