[libc++] [C++2b] [P0943] Add stdatomic.h header.
* https://wg21.link/P0943
* https://eel.is/c++draft/stdatomic.h.syn
Differential Revision: https://reviews.llvm.org/D97044
NOKEYCHECK=True
GitOrigin-RevId: 5d1c1a243c4d60249444189526ac63ced7ae999c
diff --git a/docs/FeatureTestMacroTable.rst b/docs/FeatureTestMacroTable.rst
index 8877ec0..a6c658c 100644
--- a/docs/FeatureTestMacroTable.rst
+++ b/docs/FeatureTestMacroTable.rst
@@ -342,7 +342,7 @@
------------------------------------------------- -----------------
``__cpp_lib_stacktrace`` *unimplemented*
------------------------------------------------- -----------------
- ``__cpp_lib_stdatomic_h`` *unimplemented*
+ ``__cpp_lib_stdatomic_h`` ``202011L``
------------------------------------------------- -----------------
``__cpp_lib_string_contains`` ``202011L``
------------------------------------------------- -----------------