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

[Mike Stump]

On Jul 1, 2010, at 1:07 AM, Rainer Orth wrote:
> Perhaps it would be helpful to have a new toplevel directory for
> stuff like this?

The way I think of contrib, is for stuff other than things used by make && make check && make install.  Free from the possibility to break the build, the rules for contrib can be more relaxed.