[PATCH][libstdc++-v3 parallel mode] PR 33893 work correctly even if omp_get_dynamic()

[Benjamin Kosnik]

> A few days passed since you posted the first version of the patch,
> which already contained the substantive changes, and nobody else
> commented besides me (Benjamin, in particular), therefore I assume
> there no other comments or remarks. Please commit, patch is OK.

Agreed: this general rule is much easier for everybody. 

Thanks Johannes. 

-benjamin