libprocstat(3): retrieve process command line args and environment

[Mikolaj Golub]

The updated patch set:

http://people.freebsd.org/~trociny/procstat_core.4.patch

It includes changes discussed with Kostik. New NT_PROCSTAT_PSSTRINGS
and NT_PROCSTAT_AUXV notes are added. libprocstat(3) is extended with
functions to retrieve env, args and auxv (so the patch that started
this thread a couple of months ago has been merged to this patch set
too). procstat(1) is fully converted to work only via libprocstat(3),
all its options are supported for core dumps, except kernel stacks,
which are not useful in this case.

It looks for me to be in a good shape now and I am planning to start
committing things in a week or two, after some additional testing, if
there is no objections or other suggestions.

-- 
Mikolaj Golub