I stopped my research to find out if those types ever existed in 2001. 
Clearly they do not exist now.

     libstdc++: Remove useless gdb printer registrations.

     libstdc++-v3/ChangeLog:

             * python/libstdcxx/v6/printers.py: Remove printer 
registration for non-existing
             types std::__debug::unique_ptr, std::__debug::stack, 
std::__debug::queue,
             std::__debug::priority_queue.

Ok to commit ?

François