N3644 tests for map/multimap/set/multiset. Drive-by NOEXCEPT for __tree_const_iterator constructor. Fix comment typos in other tests

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@188019 91177308-0d34-0410-b5e6-96231b3b80d8

test/containers/associative/multimap/iterator.pass.cpp

@@ -211,4 +211,18 @@ int main()
             }
     }
 #endif
+#if _LIBCPP_STD_VER > 11
+    { // N3644 testing
+        typedef std::multimap<int, double> C;
+        C::iterator ii1{}, ii2{};
+        C::iterator ii4 = ii1;
+        C::const_iterator cii{};
+        assert ( ii1 == ii2 );
+        assert ( ii1 == ii4 );
+        assert ( ii1 == cii );
+
+        assert ( !(ii1 != ii2 ));
+        assert ( !(ii1 != cii ));
+    }
+#endif
 }