[InterNetNews/inn] 3a2e41: ctlinnd: Fix a format-truncation gcc warning

[Julien ÉLIE]

  Branch: refs/heads/2.7
  Home:   https://github.com/InterNetNews/inn
  Commit: 3a2e41415bc8fae7f8b29e2b4f423677e4e89a01
      https://github.com/InterNetNews/inn/commit/3a2e41415bc8fae7f8b29e2b4f423677e4e89a01
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2023-01-08 (Sun, 08 Jan 2023)

  Changed paths:
    M innd/cc.c
    M innd/icd.c

  Log Message:
  -----------
  ctlinnd: Fix a format-truncation gcc warning

Use xasprintf() instead of snprintf().

Keep the check on the length of newsgroup names, but instead of taking the
size of a buffer, take the maximum length of an NNTP argument.