Proper C++ version detection

libuavcan/test/test_main.cpp

@@ -3,9 +3,20 @@
  */
 
 #include <gtest/gtest.h>
+#include <uavcan/impl_constants.hpp>
 
 int main(int argc, char **argv)
 {
+#ifndef UAVCAN_CPP_VERSION
+# error UAVCAN_CPP_VERSION
+#endif
+#if UAVCAN_CPP_VERSION == UAVCAN_CPP11
+    std::cout << "C++11" << std::endl;
+#elif UAVCAN_CPP_VERSION == UAVCAN_CPP03
+    std::cout << "C++03" << std::endl;
+#else
+# error UAVCAN_CPP_VERSION
+#endif
     ::testing::InitGoogleTest(&argc, argv);
     return RUN_ALL_TESTS();
 }