Prep for merging 3.4: Undo changes from 3.3 branch

docs/LanguageExtensions.rst

 =========================
 Clang Language Extensions
 =========================
 
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 Use ``__has_feature(cxx_user_literals)`` to determine if support for
 user-defined literals is enabled.
 
 C++11 variadic templates
 ^^^^^^^^^^^^^^^^^^^^^^^^
 
 Use ``__has_feature(cxx_variadic_templates)`` or
 ``__has_extension(cxx_variadic_templates)`` to determine if support for
 variadic templates is enabled.
 
-C++1y
------
-
-The features listed below are part of the committee draft for the C++1y
-standard.  As a result, all these features are enabled with the ``-std=c++1y``
-or ``-std=gnu++1y`` option when compiling C++ code.
-
-C++1y binary literals
-^^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_binary_literals)`` or
-``__has_extension(cxx_binary_literals)`` to determine whether
-binary literals (for instance, ``0b10010``) are recognized. Clang supports this
-feature as an extension in all language modes.
-
-C++1y contextual conversions
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_contextual_conversions)`` or
-``__has_extension(cxx_contextual_conversions)`` to determine if the C++1y rules
-are used when performing an implicit conversion for an array bound in a
-*new-expression*, the operand of a *delete-expression*, an integral constant
-expression, or a condition in a ``switch`` statement. Clang does not yet
-support this feature.
-
-C++1y decltype(auto)
-^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_decltype_auto)`` or
-``__has_extension(cxx_decltype_auto)`` to determine if support
-for the ``decltype(auto)`` placeholder type is enabled.
-
-C++1y default initializers for aggregates
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_aggregate_nsdmi)`` or
-``__has_extension(cxx_aggregate_nsdmi)`` to determine if support
-for default initializers in aggregate members is enabled.
-
-C++1y generalized lambda capture
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_generalized_capture)`` or
-``__has_extension(cxx_generalized_capture`` to determine if support for
-generalized lambda captures is enabled
-(for instance, ``[n(0)] { return ++n; }``).
-Clang does not yet support this feature.
-
-C++1y generic lambdas
-^^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_generic_lambda)`` or
-``__has_extension(cxx_generic_lambda)`` to determine if support for generic
-(polymorphic) lambdas is enabled
-(for instance, ``[] (auto x) { return x + 1; }``).
-Clang does not yet support this feature.
-
-C++1y relaxed constexpr
-^^^^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_relaxed_constexpr)`` or
-``__has_extension(cxx_relaxed_constexpr)`` to determine if variable
-declarations, local variable modification, and control flow constructs
-are permitted in ``constexpr`` functions.
-Clang's implementation of this feature is incomplete.
-
-C++1y return type deduction
-^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_return_type_deduction)`` or
-``__has_extension(cxx_return_type_deduction)`` to determine if support
-for return type deduction for functions (using ``auto`` as a return type)
-is enabled.
-Clang's implementation of this feature is incomplete.
-
-C++1y runtime-sized arrays
-^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_runtime_array)`` or
-``__has_extension(cxx_runtime_array)`` to determine if support
-for arrays of runtime bound (a restricted form of variable-length arrays)
-is enabled.
-Clang's implementation of this feature is incomplete.
-
-C++1y variable templates
-^^^^^^^^^^^^^^^^^^^^^^^^
-
-Use ``__has_feature(cxx_variable_templates)`` or
-``__has_extension(cxx_variable_templates)`` to determine if support for
-templated variable declarations is enabled.
-Clang does not yet support this feature.
-
 C11
 ---
 
 The features listed below are part of the C11 standard.  As a result, all these
 features are enabled with the ``-std=c11`` or ``-std=gnu11`` option when
 compiling C code.  Additionally, because these features are all
 backward-compatible, they are available as extensions in all language modes.
 
 C11 alignment specifiers
 ^^^^^^^^^^^^^^^^^^^^^^^^
@@ skipping 1210 matching lines @@
      void foo(const char* s, char *buf, ...) {
        va_list ap;
        va_start(ap, buf);
 
        vprintf(s, ap); // warning
      }
 
    In this case Clang does not warn because the format string ``s`` and
    the corresponding arguments are annotated.  If the arguments are
    incorrect, the caller of ``foo`` will receive a warning.