Pull triviality type traits into internal type_traits header

include/boost/unordered/detail/foa/core.hpp

@@ -1044,13 +1044,7 @@ struct table_arrays
       arrays.groups(),groups_size,
       std::integral_constant<
         bool,
-#if BOOST_WORKAROUND(BOOST_LIBSTDCXX_VERSION,<50000)
-      /* std::is_trivially_default_constructible not provided */
-      std::is_default_constructible<group_type>::value&&
-      std::has_trivial_default_constructor<group_type>::value
-#else
-      std::is_trivially_default_constructible<group_type>::value
-#endif 
+        is_trivially_default_constructible<group_type>::value
       >{});
     arrays.groups()[groups_size-1].set_sentinel();
   }
@@ -2024,14 +2018,7 @@ private:
       x,
       std::integral_constant<
         bool,
-#if BOOST_WORKAROUND(BOOST_LIBSTDCXX_VERSION,<50000)
-        /* std::is_trivially_copy_constructible not provided */
-        std::is_copy_constructible<element_type>::value&&
-        std::has_trivial_copy_constructor<element_type>::value
-#else
-        std::is_trivially_copy_constructible<element_type>::value
-#endif
-        &&(
+        is_trivially_copy_constructible<element_type>::value&&(
           is_std_allocator<Allocator>::value||
           !alloc_has_construct<Allocator,value_type*,const value_type&>::value)
       >{}
@@ -2074,13 +2061,7 @@ private:
 
   void copy_groups_array_from(const table_core& x) {
     copy_groups_array_from(x, std::integral_constant<bool,
-#if BOOST_WORKAROUND(BOOST_LIBSTDCXX_VERSION,<50000)
-      /* std::is_trivially_copy_assignable not provided */
-      std::is_copy_assignable<group_type>::value&&
-      std::has_trivial_copy_assign<group_type>::value
-#else
-      std::is_trivially_copy_assignable<group_type>::value
-#endif
+      is_trivially_copy_assignable<group_type>::value
       >{}
     );
   }