While we take pride in having no spinlocks in the system, if an application
wants to use them, who are we to deny them this god given right? Some
applications will implement spinlocks through a pthread interface, which is
what I implement here.

We did not have any standard trylock mechanism, so one is provided. Other than
that, the interface is pretty trivial except for the fact that it seems to
provide some protection against deadlocks. We will just ignore that for the
moment and assume a well behaved application.

Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>