CLN: In C-code: Remove unused function, init variable and fix 'strncpy maxlen'

[KetilN]

This is related to #904.

There are still macOS-related tasks left in #904.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (a777a29) 79.97% compared to head (83d8911) 79.97%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1063 +/- ## ======================================= Coverage 79.97% 79.97% ======================================= Files 94 94 Lines 13573 13573 Branches 2246 2246 ======================================= Hits 10855 10855 Misses 1976 1976 Partials 742 742 ```

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