Add syslog and fatal signal handler feature

I see random ENOTCONN failures in xfstest generic/013 and generic/014
in my branch, but earliest on the 2nd run - takes ~12hours to get
the issue, but then there are no further information logged.
ENOTCONN points to a daemon crash - I need backtraces and a core dump.

This adds optional handling of fatal signals to print a core dump
and optional syslog logging with these new public functions:

fuse_set_fail_signal_handlers()
    In addition to the existing fuse_set_signal_handlers(). This is not
    enabled together with fuse_set_signal_handlers(), as it is change
    in behavior and file systems might already have their own fatal
    handlers.

fuse_log_enable_syslog
    Print logs to syslog instead of stderr

fuse_log_close_syslog
    Close syslog (for now just does closelog())

Code in fuse_signals.c is also updated, to be an array of signals,
and setting signal handlers is now down with a for-loop instead
of one hand coded set_one_signal_handler() per signal.

1 files changed, 8 insertions, 0 deletions

diff --git a/ChangeLog.rst b/ChangeLog.rst
index cab3e81..0ed7d78 100644
--- a/ChangeLog.rst
+++ b/ChangeLog.rst
@@ -1,3 +1,11 @@
+libfuse 3.17 (unreleased)
+========================
+
+* Allows to handle fatal signals and to print a backtrace.
+  New public function: fuse_set_fail_signal_handlers()
+* Allows fuse_log() messages to be send to syslog instead of stderr
+  New public functions: fuse_log_enable_syslog() and fuse_log_close_syslog()
+
 libfuse 3.16.2 (2023-10-10)
 ===========================