[patch] Make std::tr1::shared_ptr thread-safe.

[Paolo Carlini]

Alexander Terekhov wrote:

>It won't work on Itanic (with pthread_mutex_lock/pthread_mutex_unlock
>impls NOT injecting "mf") even if GCC would "implement" all sorts of 
>MT constraints as full-stop bidirectional asm-volatile-with-memory-
>clobber-or-whatnot fence silliness as it, in fact, does currently 
>(unless I've just missed something) apart from data-dependent stuff
>(because it doesn't do data-dependent reordering stuff like value 
>prediction which hardware can do).
>  
>
Sh*t! Thanks a lot for the interesting technical details.

Paolo.