Disable all lock elision unless --enable-lock-elision=yes

[Andi Kleen]

> Andi,
> 
> Thanks. I'll get that checked in shortly. I just wanted to make
> sure that we weren't doing it for any other reason.
> 
> I'll adjust the wording of the configure switch to indicate it
> is for all elision usage in the library.

Ok.

BTW I doubt it's really needed for the systemd problems,
as systemd afaik doesn't use rwlocks.

-Andi