RFC: add a testsuite for libstdc++ pretty-printers

[Tom Tromey]

Tom> Any comments on this?

Tom> I'd like to get it in; Phil found a bug in the std::tuple printer, and
Tom> it would be nice to put in a test case along with the fix.

Benjamin> Hey Tom (and Phil!).

Benjamin> Sorry for the delay: this looks fine. Please put it in on trunk and
Benjamin> enjoy your vacation!

Thanks, I checked it in.  Let me know if there are problems.

Tom