[PATCH, libstdc++] Protect thread tests with #ifdef __GTHREADS

[Paolo Carlini]

David Edelsohn wrote:

>	A number of libstdc++ testcases are failing on AIX because the
>testcases reference specializations that only are present when __GTHREADS
>is defined.  This patch protects the tests with #ifdef __GTHREADS so that
>they compile and run when __GTHREADS is not defined.
>
>Okay for mainline?
>  
>
In the light of Benjamin's comment, I'm not convinced that this is the
best fix (indeed, would work)... or you already figured out privately
with Benjamin additional details that I'm missing? In that case ok with
me, otherwise, please help me understanding *why* on AIX we are running
those tests in the first place.

Paolo.