config.h support removed as it causes issues with compiler-explorer

src/include/units/bits/hacks.h

@@ -22,22 +22,10 @@
 
 #pragma once
 
-#include <units/bits/config.h>
 #include <experimental/ranges/concepts>
 
 namespace std {
 
-#ifndef UNITS_HAS_STD_TYPE_IDENTITY
-
-  // type_identity
-  template<typename T>
-  struct type_identity { using type = T; };
-
-  template<typename T>
-  using type_identity_t = typename type_identity<T>::type;
-
-#endif // UNITS_HAS_STD_TYPE_IDENTITY
-
   // concepts
   using experimental::ranges::same_as;
   using experimental::ranges::derived_from;