libstdc++ XPASS's on Darwin

[Joe Buck]

On Thu, Aug 17, 2006 at 08:51:04PM +0200, Paolo Carlini wrote:
> ... just an obvious remark, then I leave the issue to the darwin 
> maintainers, of course: if some, probably most, of those XPASS are 
> because of a more recent release of the OS, and the previous ones are 
> still widespread and supported, I'm not sure you really want to see 
> FAILs on the latter...

Can the test framework distinguish based on the OS release?  Probably
not with sufficient granularity, I suppose.

It seems like we need something autoconf-like for the test suite: first
you run a test for missing OS features or known flaws, then you use that
to adjust your notion of which tests are expected to pass.