wesnoth: backport gcc-13 fix

Without the change `wesnoth` fails to build against `gcc-13` as:

    $ nix build --impure --expr 'with import <nixpkgs> {}; wesnoth.override { stdenv = gcc13Stdenv; }' -L

    In file included from /build/source/src/serialization/base64.cpp:16:
    /build/source/src/serialization/base64.hpp:23:49: error: 'uint8_t' was not declared in this scope
       23 | using byte_string_view = std::basic_string_view<uint8_t>;
          |                                                 ^~~~~~~
    /build/source/src/serialization/base64.hpp:20:1: note: 'uint8_t' is defined in header '<cstdint>'; did you forget to '#include <cstdint>'?
       19 | #include <vector>
      +++ |+#include <cstdint>
       20 |

0 files changed, 0 insertions, 0 deletions