Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

Replace strlen(_PATH_DEV) with sizeof(_PATH_DEV) - 1.

Suggested by: kib
Approved by: kib (mentor)
MFC after: 5 days

- Remove gc_argname field. It was introduced for gpart(8), but if I
understand everything correctly, we don't really need it.
- Provide default numeric value as strings. This allows to simplify
a lot of code.
- Bump version number.

Add gpart(8).

In order to support gpart(8), geom(8) needs to support a named
argument. Also, optional string parameters are a requirement.
Both have been added to the infrastructure. The former required
all existing classes to be adjusted.

- Protect against specifing journal less than 100MB and against journal
which size is not multiple of sector size.

Reported by: Eric Anderson <anderson@centtech.com>

- Improve wording in error message. I'm sorry, I don't remember who
submitted this one.

Fix powerpc build.

Reported by: Peter Grehan <grehan@freebsd.org>

Add userland control utility for gjournal GEOM class.

Sponsored by: home.pl