ULogger console: using std::cerr by default to avoid ROS2 default buffering on cout/printf.

utilite/src/ULogger.cpp

@@ -25,6 +25,7 @@
 #include <fstream>
 #include <string>
 #include <string.h>
+#include <iostream>
 
 #ifndef _WIN32
 #include <sys/time.h>
@@ -93,7 +94,7 @@ private:
     }
     virtual void _writeStr(const char* msg)
 	{
-		printf("%s", msg);
+		std::cerr << msg;
 	}
 };