Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r226396:

Fix whitespace inconsistencies in systat(1).

According to md5(1), the resulting binary is the same.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

- Handle the case where interface from "middle" is missing by
more carefully inspecting the return value from sysctl(3). [1]
- Use calloc instead of malloc+memset of zero.

Submitted by: Alexander Chernikov <admin su29 net> [1]
PR: bin/119581
MFC after: 2 weeks

Remove a wrong "const" qualifier.

Spotted by: WARNS=6

Drop useless #includes.

Remove trailing whitespace.

Submitted by: Se=E1n Farley <sean-freebsd at farley dot org>
PR: bin/81874

Show the load average in the tcp display (it was already shown, perhaps
not very usefully, in all other displays). This was the original point
of the PR.

Move the load average up by 2 so that it starts in row 0 for all windows
(2 lines above it were wasted for all other windows except vmstat).
Move everything below it up by 2 or 3 (3 for icmp and icmp6 which had
an extra blank line due from not compensating for the foot-shooting in
note (3); only ip and ip6 compensated). Reduce the magic numbers related
to this.

Notes by the submitter:
%%%
1. All the subwin() calls are identical using #define MAINWIN_ROW 3
(systat.h).
2. The load average is at the top of the window.
3. Each display starts on the fourth line. I made changes to those
displays that shifted the start line (i.e., icmp). This entailed a
lot of changes within the comments at the top of those displays.
4. For ip6, I shifted the "Input next-header histogram" column down one
row to separate it from "IPv6 Output". I raised "bad scope packets"
and "address selection failed" up one row to stay with "IPv6 Input"
(valid?). They were down one row to probably line up at the bottom,
but I think they should stick with their fellow items in a column.
5. I condensed ifstat a bit. It had a lot of empty rows.
%%%

Submitted by: Se=E1n Farley <sean-freebsd at farley dot org>
PR: bin/81874

Fix the easy warnings:

1) Avoid shadowing index.
2) Constness.
3) Missing prototype for ifcmd.
4) Missing include of string.h.
5) Avoid shadowing error function.
6) ANSI definition for main.

Add "ifstat" display:

ifstat Display the network traffic going through active interfaces
on the system. Idle interfaces will not be displayed until
they receive some traffic.

For each interface being displayed, the current, peak and
total statistics are displayed for incoming and outgoing
traffic. By default, the ifstat display will automatically
scale the units being used so that they are in a human-read-
able format. The scaling units used for the current and peak
traffic columns can be altered by the scale command.

Submitted by: Trent Nelson <trent@arpa.com>