<concepts> header + std::common_reference ported from VC++

[Jonathan Wakely]

On 10/09/19 10:01 +0100, Jonathan Wakely wrote:
>On 10/09/19 08:50 +0000, sotrdg sotrdg wrote:
>>Hello everyone.
>>
>>I have ported the <concepts> header from VC++. Please add this <concepts> header in gcc 10.0.
>>
>>https://bitbucket.org/ejsvifq_mabmip/gcc-concepts-header/src/master/
>
>What license is the original code under?
>Who is the author of that code? Do you have permission to contribute
>it to GCC?
>
>I'm guessing the answer is no. There is no way we can accept a
>contribution like this. See https://gcc.gnu.org/contribute.html#legal
>for more information.
>
>Anyway, I already have an implementation of common_reference and
>various parts of the <concepts> header ready to commmit. I'm busy
>writing the tests still. I see proper tests are missing from your
>repo.

std::common_reference has been committed as r275593.