[v3] libstdc++/50196 - enable std::thread, std::mutex etc. on darwin

[Iain Sandoe]

Hi Jonathan,

On 22 Oct 2011, at 22:54, Jonathan Wakely wrote:

> I've committed this, if I've broken anything for non-POSIX platforms
> there will be time to fix it before 4.7

At present, (180333-180339) these tests seem to be failing on *- 
darwin{9,10} (which are posix) - with the failure owing to a missing  
emulated TLS variable.

e.g:
   "___emutls_v._ZSt15__once_callable", referenced from:
       ___emutls_v._ZSt15__once_callable$non_lazy_ptr in ccV8obVS.o
ld: symbol(s) not found

I haven't tried on another emulated TLS platform, but usually they  
break together - any ideas, or should I just file a PR?
cheers
Iain