[libc++] [P1065] Constexpr invoke, reference_wrapper, mem_fn, not_fn, default_searcher.

This completes the implementation of P1065 "constexpr INVOKE":
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1065r2.html

This doesn't yet complete the implementation of P1032 "Misc constexpr bits,"
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1032r1.html
but it does complete all of the <functional> bits, which means
that we can now set `__cpp_lib_constexpr_functional` for C++20.

This could use more constexpr tests for `std::reference_wrapper<T>`,
but the existing tests are extremely non-constexpr-friendly and
so I don't want to get into that rabbit-hole today.

Differential Revision: https://reviews.llvm.org/D93815

GitOrigin-RevId: 7b00e9fae3853d4693e608cc52f6d6da5059f5ff
diff --git a/include/version b/include/version
index e32f47a..dde6ca1 100644
--- a/include/version
+++ b/include/version
@@ -46,8 +46,7 @@
 __cpp_lib_complex_udls                                  201309L <complex>
 __cpp_lib_concepts                                      201806L <concepts>
 __cpp_lib_constexpr_dynamic_alloc                       201907L <memory>
-__cpp_lib_constexpr_misc                                201811L <array> <functional> <iterator>
-                                                                <string_view> <tuple> <utility>
+__cpp_lib_constexpr_functional                          201907L <functional>
 __cpp_lib_constexpr_numeric                             201911L <numeric>
 __cpp_lib_constexpr_swap_algorithms                     201806L <algorithm>
 __cpp_lib_constexpr_utility                             201811L <utility>
@@ -254,7 +253,7 @@
 # endif
 // # define __cpp_lib_concepts                             201806L
 # define __cpp_lib_constexpr_dynamic_alloc              201907L
-// # define __cpp_lib_constexpr_misc                       201811L
+# define __cpp_lib_constexpr_functional                 201907L
 # define __cpp_lib_constexpr_numeric                    201911L
 // # define __cpp_lib_constexpr_swap_algorithms            201806L
 # define __cpp_lib_constexpr_utility                    201811L