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)

Keep all convtbl-related constants and strings in convtbl.[ch].

Return back one initializer, it is needed.

+ Drop useless initializers.
+ style(9).

Drop useless #includes.

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>