Adds signal number format to kern.corefile

[leimy2k_gmail.com]

Summary

Add format capability to core file names to include signal
that generated the core. This can help various validation workflows
where all cores should not be considered equally (SIGQUIT is often
intentional and not an error unlike SIGSEGV or SIGBUS)

Submitted By: David Leimbach ([e-mail])

[leimy2k_gmail.com]

I realize procstat can list out the signal from a core file using ELF hints, but some workflows where I work use compressed corefiles, and the work to decompress them vs scanning the filename is obviously a lot more.

[leimy2k_gmail.com]

Did some basic testing with the following code.

#include <sys/types.h>
#include <signal.h>
#include <unistd.h>

int main () {
    kill(getpid(), 3);
    return 0;
}

And used:

sudo sysctl kern.corefile="%N_sig%S.core"

Ended up with

-rw-------   1 leimy  leimy  8966144 Jul 11 17:45 a.out_sig3.core

[markj]

sys/kern/kern_sig.c

3488 ↗

(On Diff #59808)

This case should be sorted before 'U'.

[vangyzen]

sys/kern/kern_sig.c

3488 ↗

(On Diff #59808)

In the man page, too.

[leimy2k_gmail.com]

Fix the sort order

[leimy2k_gmail.com]

Make man page sort order match code sort order.

[leimy2k_gmail.com]

Fixed up the sort order per review feedback.