…ble'

Most other util-linux tools that accept the option argument "auto"
additionally accept "always" and "never", not "enable" / "disable".

So, make option --cpu-stat accept those standard words (besides the
deviant ones), and adjust the documentation to use the standard words.

Furthermore, make --cpu-stat accept also "on", "off", "yes", "no",
"1", and "0", to allow the user to use shorter words.  The per-CPU
stats can now be suppressed with a succinct: `irqtop -c0`.

CC: Zhenwei Pi <pizhenwei@bytedance.com>
Signed-off-by: Benno Schulenberg <bensberg@telfort.nl>

Calling gettext() is somewhat costly: it has to find the given message
among the more than five thousand messages in util-linux's repertoire.
So, call gettext() only when the message actually gets printed.

Besides, allowing to customize the error message for parse_switch() was
a nice gesture, but it's unneeded: a fixed error message is good enough.

Also, "argument error" was rather vague, as it doesn't say _what_ the
error is.  Better say "unsupported argument".

Signed-off-by: Benno Schulenberg <bensberg@telfort.nl>

Signed-off-by: Karel Zak <kzak@redhat.com>