[Patch] Fix libstdc++/11352

[Paolo Carlini]

B. Kosnik wrote:

>>Well, the problem is, doesn't fail for me without the patch :(
>>Shall I add it anyway?
>>    
>>
>Hmmm. If you can, try to find something that can actually reproduce this
>error, and add it. (You might try switching unbuffered to on: from a
>quick look, it looks like this might do it for mainline.)
>
Ok, will do my best.

>Does this test case reproduce with a hard fail on the 3.3 branch?
>
Not for me (my system is custom and definitely not one of those 
mentioned by submitter). Besides, according to submitter, the testcase 
requires -g3 -O0...

Paolo.