Basic/type_traits: use __has_feature or __has_keyword

That potentially makes these checks more future-proof in case more edge cases are introduced on different platforms.

Author: MaxDesiatov

include/swift/Basic/type_traits.h

@@ -49,7 +49,7 @@ struct IsTriviallyConstructible {
 #if defined(_LIBCPP_VERSION) || SWIFT_COMPILER_IS_MSVC
   // libc++ and MSVC implement is_trivially_constructible.
   static const bool value = std::is_trivially_constructible<T>::value;
-#elif __has_keyword(__is_trivially_constructible)
+#elif __has_feature(is_trivially_constructible) || __has_keyword(__is_trivially_constructible)
   static const bool value = __is_trivially_constructible(T);
 #elif __has_feature(has_trivial_constructor) || __GNUC__ >= 5
   static const bool value = __has_trivial_constructor(T);
@@ -63,7 +63,7 @@ struct IsTriviallyDestructible {
 #if defined(_LIBCPP_VERSION) || SWIFT_COMPILER_IS_MSVC
   // libc++ and MSVC implement is_trivially_destructible.
   static const bool value = std::is_trivially_destructible<T>::value;
-#elif __has_keyword(__is_trivially_destructible)
+#elif __has_feature(is_trivially_destructible) || __has_keyword(__is_trivially_destructible)
   static const bool value = __is_trivially_destructible(T);
 #elif __has_feature(has_trivial_destructor) || __GNUC__ >= 5
   static const bool value = __has_trivial_destructor(T);