[libc++] Implement P0401R6 (allocate_at_least)

Reviewed By: ldionne, var-const, #libc

Spies: mgorny, libcxx-commits, arichardson

Differential Revision: https://reviews.llvm.org/D122877

NOKEYCHECK=True
GitOrigin-RevId: a96443eddedc250188b5e5f2b74ae1cf2baf1472
diff --git a/docs/FeatureTestMacroTable.rst b/docs/FeatureTestMacroTable.rst
index e305a78..fa5dcb1 100644
--- a/docs/FeatureTestMacroTable.rst
+++ b/docs/FeatureTestMacroTable.rst
@@ -300,7 +300,7 @@
     -------------------------------------------------------------------
     ``__cpp_lib_adaptor_iterator_pair_constructor``   ``202106L``
     ------------------------------------------------- -----------------
-    ``__cpp_lib_allocate_at_least``                   *unimplemented*
+    ``__cpp_lib_allocate_at_least``                   ``202106L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_associative_heterogeneous_erasure``   *unimplemented*
     ------------------------------------------------- -----------------
diff --git a/docs/Status/Cxx2bPapers.csv b/docs/Status/Cxx2bPapers.csv
index c0ef688..4aad9a6 100644
--- a/docs/Status/Cxx2bPapers.csv
+++ b/docs/Status/Cxx2bPapers.csv
@@ -11,7 +11,7 @@
 "`P2212R2 <https://wg21.link/P2212R2>`__","LWG","Relax Requirements for time_point::clock","February 2021","",""
 "`P2259R1 <https://wg21.link/P2259R1>`__","LWG","Repairing input range adaptors and counted_iterator","February 2021","",""
 "","","","","",""
-"`P0401R6 <https://wg21.link/P0401R6>`__","LWG","Providing size feedback in the Allocator interface","June 2021","",""
+"`P0401R6 <https://wg21.link/P0401R6>`__","LWG","Providing size feedback in the Allocator interface","June 2021","|Complete|","15.0"
 "`P0448R4 <https://wg21.link/P0448R4>`__","LWG","A strstream replacement using span<charT> as buffer","June 2021","",""
 "`P1132R8 <https://wg21.link/P1132R8>`__","LWG","out_ptr - a scalable output pointer abstraction","June 2021","",""
 "`P1328R1 <https://wg21.link/P1328R1>`__","LWG","Making std::type_info::operator== constexpr","June 2021","",""