MFH (r305414): add a toggle to show approximate swap usage.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Silence top(1) compiler warnings

The contrib/top code is no longer maintained upstream (last pulled 16 years
ago). The K&R-style followed by the code spews -Wimplicit-int and -Wreturn-type
warnings, amongst others. This silences 131 warnings with as little modification
as possible by adding necessary return types, definitions, headers, and header
guards, and missing header includes.

The 5 warnings that remain are due to undeclared ncurses references. I didn't
include curses.h and term.h because there are several local functions and macros
that conflict with those definitions.

MFC after: 3 weeks
Reviewed by: cem, ngie
Submitted by: Randy Westlund <rwestlun@gmail.com>
Differential Revision: https://reviews.freebsd.org/D6468

- Add J command to help.

MFC after: 2 weeks
X-MFC-with: r265249

Add "pid" to the help menu (sort keys section).

Allow per-CPU statistics to be toggled at runtime via the 'P' key.
While here, make -P a toggle similar to other options such as -I.

Reviewed by: arundel
MFC after: 1 week

Add a new option to toggle the display of the system idle process (per-CPU
idle threads). The process is displayed by default (subject to whether or
not system processes are displayed) to preserve existing behavior. The
system idle process can be hidden via the '-z' command line argument or the
'z' key while top is running. When it is hidden, top more closely matches
the behavior of FreeBSD <= 4.x where idle time was not accounted to any
process.

MFC after: 2 weeks

Add 'jid' as a possible sort order to the help screen.

PR: bin/150992
Submitted by: Frederic Culot <frederic at culot dot org>
Approved by: avg (mentor)
MFC after: 5 days

- s/jail id/jail ID/, acronyms should be in uppercase in general. Also,
it is written this way in jail(8).

Suggested by: brueffer
Approved by: delphij (mentor, implicit)

- Add documentation notes for the 'a' option, forgotten in the previous
commit.

commands.c [1]
top.X

Suggested by: rafan [1]

- Add a new 'j' switch and runtime option to toggle display jail id for
each process.
- While I'm here, keep help message sorted by keys

PR: 98489, 98975
Submitted by: clsung
Approved by: delphij (mentor)
MFC after: 2 weeks

Merge the CPU and WCPU columns in a single %6.2f column, add a new 'C'
command that toggles between the two and update the ORDER_PCTCPU()
macro to sort correctly by the visible "cpu" value.

This saves 6 more columns in 80-column terminals, making things a lot
better for the COMMAND column.

Tested on: i386, sparc64 (panther), amd64 (sledge)
Approved by: davidxu (in principle)

- Add a THR column to the process listing, that shows the number of
threads a process has. The THR column is disabled and disappears
when 'H' is hit, because then every thread gets its own output line.
- Allow sorting processes by "threads".

Approved by: davidxu
Inspired by: Jiawei Ye <leafy7382@gmail.com>

This patch merges the sort fields for both pages, so you can (for
example) view io stats while sorting by process size. Also adds
voluntary and involuntary context-switch stats to the io page because
there was lots of room.

Submitted by: Dan Nelson dnelson at allantgroup.com

document the 'I' and 't' commands in the help screen in top(1).

Submitted by: Alex Vasylenko lxv omut.org

Make 'S' in interactive mode toggle display of system processes.

Build upon the nice work of Alfred and add sorting capabilities to
the -m "io" mode of top.

Approved by: alfred

Changes to allow top to decide whether or not to show multiple threads per
process. Option -H enables it and it is toggled at the interactive
screen by 'H'.

Submitted by: Jung-uk Kim <jkim@niksun.com>

Resolve conflict: We made a fix renaming a structure member error,
but it was renamed errnum on the vendor branch.

Merge from stable: support for the o, order, command

Declared version_string() properly (1970's style).

Reviewed by: William LeFebvre <wnl@groupsys.com>
Change errno -> error in local structure to avoid a clash with the
thread-aware version of errno which is required for a thread-safe libc.

Have discussed this with the author and he has agreed to this change. 8-)

This commit was generated by cvs2svn to compensate for changes in r24139,
which included commits to RCS files with non-trunk default branches.

This is the long-awaited import of top into the base system (actually,
the src/contrib/top part right now). This tools is simply too system-
dependant to maintain it in the ports collection.