A recent change caused a performance regression. This restores the
previous performance and adds a performance test.
* scripts/check_performance: Allow tests to choose a -std flag.
* src/c++17/memory_resource.cc (bitset::get_first_unset()): Use local
variables of the right types. Call update_next_word() unconditionally.
* testsuite/20_util/unsynchronized_pool_resource/cons.cc: New test.
* testsuite/performance/20_util/memory_resource/pools.cc: New test.
* testsuite/util/testsuite_performance.h (time_counter): Allow
timer to be restarted.
From-SVN: r266164
