Merge branch 'atomics' of https://github.com/bvanassche/fio

Merge branch 'atomics' of https://github.com/bvanassche/fio

* 'atomics' of https://github.com/bvanassche/fio:
  Optimize fio_gettime_offload()
  Optimize the seqlock implementation
  Add a test that sets gtod_cpu=1
  t/run-fio-tests.py: Increase IOPS tolerance further
  fio: Use atomic_load_acquire() and atomic_store_release() where appropriate
  engines/io_uring: Use atomic_{load_acquire,store_release}()
  engines/libaio: Use atomic_store_release() instead of read_barrier()
  arch/arch.h: Introduce atomic_{load_acquire,store_release}()
  fio_sem: Remove a read_barrier() call
  Make __rand_0_1() compatible with clang
  configure: Use -Wimplicit-fallthrough=2 instead of -Wimplicit-fallthrough=3