fixed_string: manually copy string data to avoid <algorithm>

cruft/util/fixed_string.hpp

@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include <algorithm>
+#include <string_view>
 
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -30,7 +30,8 @@ namespace cruft {
         constexpr
         fixed_string (char const _value[N+1]) noexcept
         {
-            std::copy_n (_value, N, value);
+            for (std::size_t i = 0; i <= N; ++i)
+                value[i] = _value[i];
         }
 
         constexpr operator char const* () const { return value; }