[build, doc, v3] Support Sun symbol versioning in libstdc++-v3, rev. 2

[Rainer Orth]

Hi Paolo,

>> Could you please test this for me?  I don't have ready access to
>> GNU/Linux.
>>   
> The patch apparently works, I'm finishing regtesting it but abi_check is
> back to normality.

let me know when you're done and I'll commit it.

>> Sorry for the mess.
>>   
> No problem, your contribution is certainly welcome, but please, in the
> future, make sure to *somehow* test on linux too, where versioning s vital.

Ok, I'll see what I can do with either VirtualBox or the test farm.

	Rainer

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Rainer Orth, Center for Biotechnology, Bielefeld University