Reland [libc++] [P0325] Implement to_array from LFTS with updates.

Fixed expected errors and notes.

Summary:
This patch implements https://wg21.link/P0325.

Reviewers: EricWF, mclow.lists, ldionne, lichray

Reviewed By: ldionne, lichray

Subscribers: lichray, dexonsmith, zoecarver, christof, ldionne, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D69882

Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: e93e58c6c40a365bc9275dd8a8242598343cc835
diff --git a/docs/FeatureTestMacroTable.rst b/docs/FeatureTestMacroTable.rst
index 3dd00fa..a02e727 100644
--- a/docs/FeatureTestMacroTable.rst
+++ b/docs/FeatureTestMacroTable.rst
@@ -199,6 +199,8 @@
     ``__cpp_lib_ranges``                              *unimplemented*  
     ------------------------------------------------- -----------------
     ``__cpp_lib_three_way_comparison``                *unimplemented*  
+    ------------------------------------------------- -----------------
+    ``__cpp_lib_to_array``                            ``201907L``      
     ================================================= =================