Inline namespaces are always available in Clang. Rely on that without

testing via __has_feature, since __has_feature for C++0x features no
longer evaluates true in C++98/03 mode.

Also, eliminate the redundant using directive. Inline namespaces make
their members visible in the enclosing namespace automatically.



git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@124293 91177308-0d34-0410-b5e6-96231b3b80d8

include/__config

@@ -148,22 +148,15 @@ typedef __char32_t char32_t;
 #define _LIBCPP_HAS_NO_TRAILING_RETURN
 #endif
 
-#if __has_feature(cxx_inline_namespaces)
+// Inline namespaces are available in Clang regardless of C++ dialect.
 #define _LIBCPP_BEGIN_NAMESPACE_STD namespace std {inline namespace _LIBCPP_NAMESPACE {
 #define _LIBCPP_END_NAMESPACE_STD  } }
 #define _STD std::_LIBCPP_NAMESPACE
 
 namespace std {
-inline namespace _LIBCPP_NAMESPACE {
+  inline namespace _LIBCPP_NAMESPACE {
+  }
 }
-using namespace _LIBCPP_NAMESPACE;
-}
-
-#else  // __has_feature(cxx_inline_namespaces)
-#define _LIBCPP_BEGIN_NAMESPACE_STD namespace std {
-#define _LIBCPP_END_NAMESPACE_STD }
-#define _STD std
-#endif  // __has_feature(cxx_inline_namespaces)
 
 #if !(__has_feature(cxx_constexpr))
 #define _LIBCPP_HAS_NO_CONSTEXPR