3 libstdc++ tests fail at random

[Uros Bizjak]

Hello!

> I have been seeing 3 libstdc++ tests:
>
> FAIL: 17_intro/headers/c++200x/stdc++.cc (test for excess errors)
> FAIL: 17_intro/headers/c++200x/stdc++_multiple_inclusion.cc (test for excess errors)
> FAIL: 30_threads/async/async.cc execution test
>
> fail/pass at random on a fast machine.  Is this expected?

Please see PR 59436 [1] for the first two failures.

[1] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59436

Uros.