Implement IP_STAT+IP_STATUS (aliases of the same format) on NetBSD

Implement IP_STAT+IP_STATUS (aliases of the same format) on NetBSD

Output based on FreeBSD with the following changes:
 - "utime+stime, children" merged from "utime, children" and
   "stime, children".
 - "Minor faults, children", "Major faults, children",
   "Virtual memory size" removed as not available in a direct
   equivalent.

No new values missing or skipped in FreeBSD are printed, although
there is a long list of potential candiates.

gdb/ChangeLog:

        * nbsd-nat.c (nbsd_pid_to_kinfo_proc2): New.
        (nbsd_nat_target::info_proc): Add do_status.