libstdc++ testsuite make targets check-parallel and check-performance don't work anymore

[Paolo Carlini]

.. other than the above issue, I see a segmentation fault for:

     performance/ext/pb_ds/multimap_text_insert_mem_large.cc

and a compile error for:

     performance/ext/pb_ds/priority_queue_text_pop_mem.cc

which boils down to a an error at include/bits/stl_deque.h:519 (likely 
pd_ds is misusing std::deque). Jon, can you double check the latter?

Thanks,
Paolo.