Print MB and GB instead of MiB and GiB mislabeled as MB and GB.
SD cards are sold in GB not GiB, this will result in less confusion.
Also, cache parent device pointer to save a few cycles for loops.
Re-factor coredump routines.  For each type of notes an output
function is provided, which is used either to calculate the note size
or output it to sbuf.  On the first pass the notes are registered in a
list and the resulting size is found, on the second pass the list is
traversed outputing notes to sbuf.  For the sbuf a drain routine is
provided that writes data to a core file.

The main goal of the change is to make coredump to write notes
directly to the core file, without preliminary preparing them all in a
memory buffer.  Storing notes in memory is not a problem for the
current, rather small, set of notes we write to the core, but it may
becomes an issue when we start to store procstat notes.

Reviewed by:	jhb (initial version), kib
Discussed with:	jhb, kib
MFC after:	3 weeks
Re-factor the code to provide kern_proc_filedesc_out(), kern_proc_out(),
and kern_proc_vmmap_out() functions to output process kinfo structures
to sbuf, to make the code reusable.

The functions are going to be used in the coredump routine to store
procstat info in the core program header notes.

Reviewed by:	kib
MFC after:	3 weeks
Similarly to proc_getargv() and proc_getenvv(), export proc_getauxv()
to be able to reuse the code.

MFC after:	3 weeks