Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Further simplify the code, and update the manpage.

Submitted by: Christoph Mallon <christoph.mallon@gmx.de>

Constify the first argument to expand_number() so that it can
be called with a const without the compiler grisling.

Adjust history.

Approved by: re(ken)

Point expand_number(3) at humanize_number(3) and nive versa.

Suggested by: trhodes
Approved by: re (kensmith)

Implement expand_number(3), which is the opposite of humanize_number(3), ie.
a number in human-readable form is converted to int64_t, for example:
123b -> 123
10k -> 10240
16G -> 17179869184

First version submitted by: Eric Anderson <anderson@freebsd.org>
Approved by: re (bmah)