* src/atomic_ops.c (AO_USE_NO_SIGNALS, AO_USE_NANOSLEEP): New
macros.
* src/atomic_ops.c (AO_USE_WIN32_PTHREADS): Imply
AO_USE_NO_SIGNALS.
* src/atomic_ops.c: Don't include signal.h if AO_USE_NO_SIGNALS.
* src/atomic_ops.c: Include time.h if AO_USE_NANOSLEEP.
* src/atomic_ops.c (AO_locks, AO_pause): Reformat the code.
* src/atomic_ops.c (AO_pause): Use nanosleep() if
AO_USE_NANOSLEEP.
* src/atomic_ops.c (all_sigs, initialized,
AO_compare_and_swap_emulation,
AO_compare_double_and_swap_double_emulation): Use
AO_USE_NO_SIGNALS instead of AO_USE_WIN32_PTHREADS.