Moved exempt_ptr to observer_ptr as per
N3740 - A Proposal for the World’s Dumbest Smart Pointer, v3 - Walter E. Brown - 2014-01-01
I filled in some but I'll need to check.
Add make_array per N3824 - make_array - Zhihao Yuan - 2013-10-22
Good thread_local observation (comment) in random.
Tweaked decltype hell testers - decltype works.