Implement midpoint for floating point types. Reviewed as https://reviews.llvm.org/D61014.

llvm-svn: 359184
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: d3d0ecbfd52cca2c7e0f4478e5682c493fd99ef2
diff --git a/include/version b/include/version
index 948f645..102da67 100644
--- a/include/version
+++ b/include/version
@@ -58,6 +58,7 @@
 __cpp_lib_incomplete_container_elements                 201505L <forward_list> <list> <vector>
 __cpp_lib_integer_sequence                              201304L <utility>
 __cpp_lib_integral_constant_callable                    201304L <type_traits>
+__cpp_lib_interpolate                                   201902L <numeric>
 __cpp_lib_invoke                                        201411L <functional>
 __cpp_lib_is_aggregate                                  201703L <type_traits>
 __cpp_lib_is_constant_evaluated                         201811L <type_traits>
@@ -222,6 +223,7 @@
 // # define __cpp_lib_destroying_delete                    201806L
 # define __cpp_lib_erase_if                             201811L
 // # define __cpp_lib_generic_unordered_lookup             201811L
+# define __cpp_lib_interpolate                          201902L
 # if !defined(_LIBCPP_HAS_NO_BUILTIN_IS_CONSTANT_EVALUATED)
 #   define __cpp_lib_is_constant_evaluated              201811L
 # endif