Fix underallocation of abort_msg_s struct (CVE-2025-0395)

Fix underallocation of abort_msg_s struct (CVE-2025-0395)

Include the space needed to store the length of the message itself, in
addition to the message string.  This resolves BZ #32582.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
(cherry picked from commit 68ee0f704cb81e9ad0a78c644a83e1e9cd2ee578)

Conflict in sysdeps/posix/libc_fatal.c due to missing cleanup after
backtrace removal.

(cherry picked from commit df4e1f4a5096b385c9bcc94424cf2eaa227b3761)

Gbp-Pq: Topic any
Gbp-Pq: Name local-CVE-2025-0395-1.diff