<type_traits>: Remove _IS_LAYOUT_COMPATIBLE_SUPPORTED macro and related __builtin*() intrinsics #1637
Description
The original compiler intrinsics supporting P0466R5, were replaced by @JonCavesMSFT to better conform to the naming conventions in <type_traits>. The new names remove the "__builtin" prefix. To support the transition from the old names to the new ones, a compiler-provide macro is provided, _IS_LAYOUT_COMPATIBLE_SUPPORTED. #1575 used this macro to support both intrinsics names.
These compiler changes are expected to be included in Dev16.10 Preview 1. Once that version ships, the old names will be obsolete, and we should remove them as well and related #ifdef _IS_LAYOUT_COMPATIBLE_SUPPORTED in <type_traits>.