see #10255 comment 2
Feel free to reassign ticket to yourself if you want to make other updates.
Adjusted the config test to run with -std=C++11. Otherwise it would never succeed with compiling #include <atomic>.
Also rearranged (and hopefully simplified) the #if chain in putilimp.h. There's no longer a need for special case Macintosh tests - the autoconf test handles it correctly.