[RESEND PATCH 1/3] Mutex: Accelerate lock acquisition by queuing spinner

[Florian Weimer]

* Kemi Wang:

> +# define PTHREAD_QUEUESPINNER_MUTEX_INITIALIZER_NP \
> +  { { 0, 0, 0, PTHREAD_MUTEX_QUEUESPINNER_NP, { 0, 0, 0, 0 }, 0, \
> +      { __PTHREAD_SPINS }, { 0, 0 } } }

Is it really necessary to add the initializer?

Without it, we can remove all references to
PTHREAD_QUEUESPINNER_MUTEX_INITIALIZER_NP from the hot path in case
something better comes up.

Thanks,
Florian