* doc/ref/api-scheduling.texi (Atomics): New manual section.
* libguile.h: Include atomic.h.
* libguile/Makefile.am (libguile_@GUILE_EFFECTIVE_VERSION@_la_SOURCES):
  (DOT_X_FILES, DOT_DOC_FILES, modinclude_HEADERS): Add atomic.
* libguile/atomic.c:
* libguile/atomic.h: New files.
* libguile/atomics-internal.h (scm_atomic_set_scm, scm_atomic_ref_scm)
  (scm_atomic_swap_scm, scm_atomic_compare_and_swap_scm): New
  facilities.
* libguile/goops.c (class_atomic_box, scm_sys_goops_early_init): Add
  support for <atomic-box>.  Remove duplicate <keyword> fetch.
* libguile/init.c (scm_i_init_guile): Call scm_register_atomic_box.
* libguile/print.c (iprin1): Add atomic box case.
* libguile/tags.h (scm_tc7_atomic_box): New tag.
* libguile/validate.h (SCM_VALIDATE_ATOMIC_BOX): New macro.
* module/Makefile.am (SOURCES): Add ice-9/atomic.scm.
* module/ice-9/atomic.scm: New file.
* module/oop/goops.scm (<atomic-box>): New var.