Unordered: Merge from trunk

- Avoid an incorrect MSVC unused variable warning in the tests.
- Remove a `try..catch`.
- Adjust SFINAE use to try to supprt g++ 3.4. Fixes #7175.
- Fix some use of rvalues.
- Extra info in `at_tests`.



[SVN r79868]

test/unordered/at_tests.cpp

@@ -13,21 +13,31 @@
 namespace at_tests {
 
 UNORDERED_AUTO_TEST(at_tests) {
+    BOOST_LIGHTWEIGHT_TEST_OSTREAM << "Create Map" << std::endl;
+
     boost::unordered_map<std::string, int> x;
     typedef boost::unordered_map<std::string, int>::iterator iterator;
 
+    BOOST_LIGHTWEIGHT_TEST_OSTREAM << "Add elements" << std::endl;
+
     x["one"] = 1;
     x["two"] = 2;
 
+    BOOST_LIGHTWEIGHT_TEST_OSTREAM << "Check existing elements" << std::endl;
+
     BOOST_TEST(x.at("one") == 1);
     BOOST_TEST(x.at("two") == 2);
 
+    BOOST_LIGHTWEIGHT_TEST_OSTREAM << "Check missing element" << std::endl;
+
     try {
         x.at("three");
         BOOST_ERROR("Should have thrown.");
     }
     catch(std::out_of_range) {
     }
+
+    BOOST_LIGHTWEIGHT_TEST_OSTREAM << "Finished" << std::endl;
 }
 
 }