[patch] fix thread test cases for solaris.

[Paolo Carlini]

Andreas Tobler wrote:
> Hi all,
>
> The below test cases fail under sparc-solaris10, undefined reference
> to sched_yield or nanosleep. Those are part of librt.
>
> This simple patch makes these test cases compile and run under
> sparc-solaris10. (Not supported under solaris8)
>
> Ok for trunk?
Not Ok. We decided we don't want the user to experience in link time
errors, and those testcases, if I understand correctly, could be actual
user code snippets. Thus, we want to solve the issue at a more basic
level, that is not using inadvertently in the implementation something
which in general is available only with -lrt. Chris, can you have a look?

Paolo.