Minor cleanup for string_view; mostly from suggestions by Richard Smith. Also, make the tests pass under c++03

llvm-svn: 212185
diff --git a/libcxx/test/experimental/string.view/string.view.access/front.pass.cpp b/libcxx/test/experimental/string.view/string.view.access/front.pass.cpp
index f53dfb77..e9df44b 100644
--- a/libcxx/test/experimental/string.view/string.view.access/front.pass.cpp
+++ b/libcxx/test/experimental/string.view/string.view.access/front.pass.cpp
@@ -38,7 +38,7 @@
     assert ( test ( U"a", 1 ));
 #endif
 
-#if _LIBCPP_STD_VER > 11
+#if __cplusplus >= 201103L
     {
     constexpr std::experimental::basic_string_view<char> sv ( "ABC", 2 );
     static_assert ( sv.length() ==  2,  "" );