log used config file to debug.log on startup

src/init.cpp

@@ -614,6 +614,7 @@ bool AppInit2(boost::thread_group& threadGroup)
         LogPrintf("Startup time: %s\n", DateTimeStrFormat("%Y-%m-%d %H:%M:%S", GetTime()));
     LogPrintf("Default data directory %s\n", GetDefaultDataDir().string());
     LogPrintf("Using data directory %s\n", strDataDir);
+    LogPrintf("Using config file %s\n", GetConfigFile().string());
     LogPrintf("Using at most %i connections (%i file descriptors available)\n", nMaxConnections, nFD);
     std::ostringstream strErrors;