[PATCH][libstdc++-v3 parallel mode] PR 42712 search_n serial fallbacks

[Paolo Carlini]

Hi,
> Disclaimer: Adding a member to __gnu_parallel::_Settings may change the
> library binary.
>   
If I understand correctly what you are doing here, adding the new data
member at the *end* of the existing ones should minimize the possible
problems: I think the only existing applications that could break are
those using sizeof(_Settings), which seems really unlikely to me. Then I
would consider the trade-off vs parallel-mode stability certainly
acceptable. What do you think?

Let's wait a couple of days for other opinions... Worst case we can
hardwire 1000 with a comment, seems still an improvement vs the current
situation.

Paolo.