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: r227309 (partial)

Mark all SYSCTL_NODEs static that have no corresponding SYSCTL_DECLs.

The SYSCTL_NODE macro defines a list that stores all child-elements of
that node. If there's no SYSCTL_DECL macro anywhere else, there's no
reason why it shouldn't be static.

MFC r239021:

In virstor_ctl_stop(), check for a valid softc before trying to update
metadata.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Include sys/sbuf.h directly.

Reviewed by: pjd

Implement relaxed comparision for hardcoded provider names to make it
ignore adX/adaY difference in both directions to simplify migration to
the CAM-based ATA or back.

Add some FEATURE macros for various GEOM classes.

No FreeBSD version bump, the userland application to query the features will
be committed last and can serve as an indication of the availablility if
needed.

Sponsored by: Google Summer of Code 2010
Submitted by: kibab
Reviewed by: silence on geom@ during 2 weeks
X-MFC after: to be determined in last commit with code from this project

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

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

Prevent NULL deference by checking return value of
gctl_get_asciiparam.

MFC after: 2 weeks

Go through with write_metadata() non-error-handling and make it return "void".
This is mostly to avoid dead variable assignment warning by LLVM.
No functional change.

Pointed out by: trasz
Approved by: gnn (mentor)

Avoid NULL deference.

Reviewed by: ivoras

LINT compiled just fine for me, but it seems it breaks tinerbox way of
compiling LINT.

Approved by: re (implicitly)

Bring in the GEOM Virtualisation class, which allows to create huge GEOM
providers with limited physical storage and add physical storage as
needed.

Submitted by: Ivan Voras
Sponsored by: Google Summer of Code 2006
Approved by: re (kensmith)