[PATCH] Fix race in pthread_mutex_lock while promoting to PTHREAD_MUTEX_ELISION_NP [BZ #23275]

[Florian Weimer]

* Stefan Liebler:

> The flag PTHREAD_MUTEX_NO_ELISION_NP is not explicitly checked before
> FORCE_ELISION is called. But only one of those two flags can be set.
> Your remaining assumption is correct.
> I've changed the comment in the three force-elision.h files. Is this
> okay?

The comment looks good to me know.  Thanks!

Florian