df(1): use statvfs instead of raw disk access

As of this patch, df(1) no longer performs raw disk access; it
operates exclusively on mounted file systems. This also means
that df no longer needs to be setuid.
setup(8): only call df(1) on mounted file systems
release.sh: call df(1) with -k
Retire badblocks(8) and readall(1)
MAKEDEV(8): don't make /dev/filter user-accessible
format(1): access floppy as block device

Accessing block devices as character devices is no longer supported.
Retire checkhier(8)
mount(1): do not include system headers
mount(1)/umount(1)/format(1): remove setuid bits

This is a security measure. We may want to bring back user access to
mounting and formatting media in the future, but this should be done
only once we are sure that this is safe from a security perspective.
libvboxfs: fix setting file mtimes
mmc:driver development added dummy driver.

* Add dummy driver to allow independent testing of mmcblk.
* Always build the mmc driver to prevent breakage.
* Allow to specify the mmc driver to be used at load time.

Change-Id: I4e14b912fb8f3612e252864b53733968b23ac023
Patch mkdep to make sure tested values are not mistaken
as test flags.
Adding -nt flag to test

This is needed by build.sh.
Importing postinstall

Change-Id: I5813064164e2d6ca4cf353fb184194b2aaa8caa3
mmc:Fixes for coverity.

Change-Id: I25e406126deb9172276844e1bb756e22e1f449f8
Importing cksum (needed by NetBSD build system)

Change-Id: I47308635f6307066643f83f07b6751b1f2a05eb4
Move primary cache code to libminixfs.

Add primary cache management feature to libminixfs as mfs and ext2
currently do separately, remove cache code from mfs and ext2, and make
them use the libminixfs interface. This makes all fields of the buf
struct private to libminixfs and FS clients aren't supposed to access
them at all. Only the opaque 'void *data' field (the FS block contents,
used to be called bp) is to be accessed by the FS client.

The main purpose is to implement the interface to the 2ndary vm cache
just once, get rid of some code duplication, and add a little
abstraction to reduce the code inertia of the whole caching business.

Some minor sanity checking and prohibition done by mfs in this code
as removed from the generic primary cache code as a result:
        - checking all inodes are not in use when allocating/resizing
          the cache
        - checking readonly filesystems aren't written to
        - checking the superblock isn't written to on mounted filesystems

The minixfslib code relies on fs_blockstats() in the client filesystem to
return some FS usage information.
drivers: fix various sys_irqsetpolicy calls
mtree mknod

Change-Id: I887437c7b84839fc644da4c55bd59b6a414408ef
Fixed up new mtree description file NetBSD.dist.base (removed end of line spaces, added a few missing directories)

Fixed lchflags error under MINIX3 as host OS

Change-Id: I00f708e82753fdae85ac54bc903db06a7775ab5a