A few release notes updates for C++ support in Clang 6.0.

  conforming GNU extensions. Projects incompatible with C++14 can add

  ``-std=gnu++98`` to their build settings to restore the previous behaviour.

- Added support for some features from the C++ standard after C++14

  (provisionally known as C++2a but expected to be C++20). This support can be

  enabled with the ``-std=c++2a`` flag. This enables:

  - Support for ``__VA_OPT__``, to allow variadic macros to easily provide

    different expansions when they are invoked without variadic arguments.

  - Recognition of the ``<=>`` token (the C++2a three-way comparison operator).

  - Support for default member initializers for bit-fields.

  - Lambda capture of ``*this``.

  - Pointer-to-member calls using ``const &``-qualified pointers on temporary objects.

  All of these features other than ``__VA_OPT__`` and ``<=>`` are made

  available with a warning in earlier C++ language modes.

- A warning has been added for a ``<=`` token followed immediately by a ``>``

  character. Code containing such constructs will change meaning in C++2a due

  to the addition of the ``<=>`` operator.

- Clang implements the "destroying operator delete" feature described in C++

  committee paper `P0722R1

  <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0722r1.html>`,

  which is targeting inclusion in C++2a but has not yet been voted into the C++

  working draft. Support for this feature is enabled by the presence of the

  standard library type ``std::destroying_delete_t``.

OpenCL C Language Changes in Clang

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