newsyslog: provide -I option to specify default signal

[glebius]

Summary

Useful when used with syslog-ng, which uses SIGUSR1. Instead of adding
signal number to every new entry, just set it via command line option.

[bcr]

Minor language corrections in the man page.

usr.sbin/newsyslog/newsyslog.8

252

s/don't/do not/
s/have signal/have a signal/

253

This option accepts either a signal number or a name as argument.

254

s/Default/The default/

[glebius]

Address Benedict's review.

[bcr]

Thanks, ready to commit from my point of view.

[delphij]

I like the change in general, but if I was you I'd probably use getopt_long() and call the option --signal (consider this as an optional suggestion; I don't have strong opinion with this choice), because -I was somewhat counterintuitive to me as a flag to specify signal and both -s and -S were already occupied.

[ivy]

In D52701#1205432, @delphij wrote:

I like the change in general, but if I was you I'd probably use getopt_long() and call the option --signal (consider this as an optional suggestion; I don't have strong opinion with this choice), because -I was somewhat counterintuitive to me as a flag to specify signal and both -s and -S were already occupied.

i don't think we should be introducing mandatory non-standard GNU long options into base unless it's for compatibility with other platforms.