bin/54529: route -c option is undocumented

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         54529
>Category:       bin
>Synopsis:       route -c option is undocumented
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          doc-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Sep 06 15:00:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, among others
>Organization:

>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

The route(8) command supports a "-c" option, but it is not
documented in the man page.

The commit that added the option also changed the man page:

  2017.06.16.04.40.16 ozaki-r src/sbin/route/route.8 1.57
  2017.06.16.04.40.16 ozaki-r src/sbin/route/route.c 1.156

but that change only removed a .Pp; it did not add any new text.

>How-To-Repeat:

>Fix: