MFC r346113:
libnv: fix compilation warnings

When building libnv without a debug those arguments are no longer used
because assertions will be changed to NOP.

Submitted by: Mindaugas Rasiukevicius <rmind@netbsd.org>

MFC r304910, r304912, r304915, r304952, r325019, r328164, r331094, r332664,
r335341-r335345, r335347, r335379-r335380, r335382

r304910:
Introduce cnv man page.

r304912:
Add missed header file for cnv.h .

r304915:
Bump date in the man page.

r304952:
Remove duplicated declaration.

r325019:
Introduce cnvlist_name() and cnvlist_type() functions.

Those function can be used when we are iterating over nvlist to reduce
amount of extra variables we need to declare.

r328164:
libnv: Use mallocarray(9) for the nv_calloc.

r331094:
Fix formatting errors that resulted in apropos(1) output looking weird.

r332664:
Add missing argument in the cnv man page.

r335341:
libnv: change name of cookie from cookiep to cookie.

The name was inconsistent with rest of the library.
No functional change intended.

r335342:
libnv: add const to cookies arguments

r335343:
libnv: Remove nvlist argument from cnvlist_{take,free}_* functions.

All information which are need for those operations is already stored in
the cookie.

We decided not to bump libnv version because this API is not used yet in the
base system.

r335344:
libnv: clean parent in nvlist_array when removing it.

When we are removing element form the nvlist we should also clean parent,
because the array is not a part of the nvlist anymore.

r335345:
libnv: add regression test for r335344.

r335347:
libnv: Add nvlist_append_*_array() family of functions.

The nvlist_append_{bool,number,string,nvlist,descriptor}_array() functions
allows to dynamically extend array stored in the nvlist.

r335379:
Set prev to NULL so its garaunteed to have a value of some kind and
gcc doesn't explode. Feel free to fix this correctly or whatever for
gcc builds.

This *should* quiesce tinderbox after r335347 for the gcc builds.

r335380:
style(9) fix, I was also going to silence gcc.

r335382:
Really fix the style.

MFC r323860:
Plug memory leak in case when nvlist allocation succeeds, but nvpair
allocation fails.

Submitted by: pjd@
Sponsored by: Wheel Systems

MFC r323858:
IMHO it is possible that failure will be treated as success because we don't
initialize nvp on every loop iteration and the code under 'fail'(!) label
detects success by checking of nvp != NULL.

Submitted by: pjd@
Sponsored by: Wheel Systems

MFC r323856:
Free 'value' only once we are done freeing all individual

Submitted by: pjd@
Found by: scan-build
Sponsored by: Wheel Systems

MFC r323851:
Remove redundant initialization. Don't use variable - just return the value.
Make scan-build happy by casting to 'void *' instead of 'void **'.

Submitted by: pjd@
Found by: scan-build and cppcheck
Sponsored by: Wheel Systems

MFC r323854:
Because nvp wasn't initialized on every loop iteration once we jumped
to 'fail' on error it was treated as success, because nvp!=NULL. Fix this
by not handling success under 'fail' label and by using separate variable
for parent nvpair.

If we succeeded to allocate nvlist, but failed to allocated nvpair we
would leak nvls[ii] on return. Destroy it when we cannot allocate nvpair,
before we goto fail.

Submitted by: pjd@ and oshogbo@ (minor changes)
Found by: scan-build
Sponsored by: Wheel Systems

MFC r323853:
Make the code consistent by always using 'fail' label.

Submitted by: pjd@ and oshogbo@
Sponsored by: Wheel Systems

MFC r323859:
Simplify the code by _not_ expecting success under 'fail'.

Submitted by: pjd@ and oshogbo@
MFC after: 1 month
Sponsored by: Wheel Systems

MFC r302965:
Fix memory leak in the nvlist string array.

Submitted by: Adam Starak <starak.adam@gmail.com>
Approved by: re (gjb)