Copy the tokens of json_pointer::to_string() with std::copy

clang-tidy (bugprone-not-null-terminated-result) took the memcpy into
the result string for a C string missing its terminator. std::copy is
the same memmove; to_string() instructions are unchanged (Apple clang).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

include/nlohmann/detail/json_pointer.hpp

@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include <algorithm> // all_of
+#include <algorithm> // all_of, copy
 #include <array> // array
 #include <cctype> // isdigit
 #include <cerrno> // errno, ERANGE
@@ -104,8 +104,7 @@ class json_pointer
                 for (const auto& reference_token : reference_tokens)
                 {
                     *out++ = '/';
-                    std::memcpy(out, reference_token.data(), reference_token.size());
-                    out += reference_token.size();
+                    out = std::copy(reference_token.data(), reference_token.data() + reference_token.size(), out);
                 }
             }
             return result;