preserve_exit: Ignore SIGHUP

closes #9274
ref #9028

If stdin closed then read_error_exit calls preserve_exit. Handling
SIGHUP during preserve_exit would cause a premature teardown, and
conflicts with e.g. ui_bridge_stop which waits for TUI to teardown.

Vim ignores SIGHUP in its prepare_to_exit and getout_preserve_modified
routines:

    /* Ignore SIGHUP, because a dropped connection causes a read error, which
     * makes Vim exit and then handling SIGHUP causes various reentrance
     * problems. */
    signal(SIGHUP, SIG_IGN);

0 files changed, 0 insertions, 0 deletions