pthread_cancel and EH: let's try this again

[Alexander Terekhov]

David Abrahams wrote:
[...]
>   3. Optional: As an extension, provide a way to enable the normal 'C'
>      library to throw cancellation

That's what "-pthread" does. In (posix) threaded C/C++, normal 'C' 
library is enabled to throw cancellation unless you disable it...
intelligent cancel delivery (i.e. no delivery to std::unexpected()
on part of the implementation) aside for a moment. There's no other 
(sensible) way to resolve the issue.

regards,
alexander.