[patch] libstdc++/56117 make std::async launch new threads by default

[Jonathan Wakely]

On 02/05/15 19:56 +0100, Jonathan Wakely wrote:
>One last patch before I head to Lenexa, this fixes the long standing
>not-a-bug that our default launch policy is launch::deferred.
>
>This way std::async with no explicit policy or with any policy that
>contains launch::async will run in a new thread.
>
>Apparently libc++ does the same and they aren't getting lots of
>complaints about fork-bombs, so let's try the same thing. If people
>don't like it we have plenty of time in stage 1 to reconsider.
>
>Tested x86_64-linux and powerpc64le-linux, I'm going to commit this to
>trunk unless someone strongly objects.

Committed to trunk.