Fix coroutine detection with recent Xcode.

Author: chriskohlhoff

asio/include/asio/detail/config.hpp

@@ -2122,7 +2122,11 @@
 #     if __has_include(<coroutine>)
 #      define ASIO_HAS_CO_AWAIT 1
 #     endif // __has_include(<coroutine>)
-#    endif // (__cplusplus >= 202002) && (__cpp_impl_coroutine >= 201902)
+#    elif (__cplusplus >= 201703) && (__cpp_coroutines >= 201703)
+#     if __has_include(<experimental/coroutine>)
+#      define ASIO_HAS_CO_AWAIT 1
+#     endif // __has_include(<experimental/coroutine>)
+#    endif // (__cplusplus >= 201703) && (__cpp_coroutines >= 201703)
 #   else // (__clang_major__ >= 14)
 #    if (__cplusplus >= 201703) && (__cpp_coroutines >= 201703)
 #     if __has_include(<experimental/coroutine>)