MFC r304910, r304912, r304915, r304952, r325019, r328164, r331094, r332664,

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.