Merge commit 'eb34d403'

* commit 'eb34d403':
  Add a compat dummy stdatomic.h used when threading is disabled
  Add a compat stdatomic.h implementation based on pthreads
  Add a compat stdatomic.h implementation based on suncc atomics
  Add a compat stdatomic.h implementation based on windows atomics
  Add a compat stdatomic.h implementation based on GCC atomics

This merge is a noop, see:
  41e891e8 Add a compat dummy stdatomic.h used when threading is disabled
  74b5f108 Add a compat stdatomic.h implementation based on pthreads
  70faadc8 Add a compat stdatomic.h implementation based on suncc atomics
  c91e72ed Add a compat stdatomic.h implementation based on windows atomics
  3359eede Add a compat stdatomic.h implementation based on GCC atomics
Merged-by: Clément Bœsch <u@pkh.me>