[PING] [C++17] Implement N3928 - Extending static_assert

[Ed Smith-Rowland]

On 05/02/2015 04:16 PM, Ed Smith-Rowland wrote:
> This extends' static assert to not require a message string.
> I elected to make this work also for C++11 and C++14 and warn only 
> with -pedantic.
> I think many people just write
>   static_assert(thing, "");
> .
>
> I took the path of building an empty string in the parser in this case.
> I wasn't sure if setting message to NULL_TREE would cause sadness 
> later on or not.
>
> I also, perhaps in a fit of overzealousness made finish_static_assert 
> not print the extra ": " and an empty message in this case.
>
> I didn't modify _Static_assert for C.
>
> Built and tested on x86_64-linux.
>
> OK
>

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