vol_id - probe filesystem and read label and uuid

vol_id will only return with a non-zero exit code if the string asked for,
is not empty. All trailing whitespace will be removed, spaces replaced by
underscore and slashes ignored.
Unmangled values are available in the --export mode as hex-encoded strings
in *_ENC= keys.

  $ extras/volume_id/vol_id --export /dev/sda6
  ID_FS_USAGE=filesystem
  ID_FS_TYPE=ext3
  ID_FS_VERSION=1.0
  ID_FS_UUID=3e999973-00c9-4917-9442-b7633bd95b9e
  ID_FS_UUID_ENC=3e999973-00c9-4917-9442-b7633bd95b9e
  ID_FS_LABEL=devel
  ID_FS_LABEL_ENC=devel

  $ extras/volume_id/vol_id --label /dev/sda6
  devel

  $ extras/volume_id/vol_id --type /dev/sda6
  ext3


fstype                 probe  label  uuid  version
--------------------------------------------------
linux swap             *      *      *     *
btrfs                  *      *      *     -
ext                    *      *      *     *
reiserfs jr/3.5/3.6/4  *      *      *     *
fat (12, 16, 32)       *      *      *     *
ntfs                   *      *      *     *
jfs                    *      *      *     -
xfs                    *      *      *     -
hfs (plus, wrapped)    *      *      *     -
udf                    *      *      -     -
iso9660                *      *      -     -
ufs                    *      -      -     -
cramfs                 *      *      -     -
sysv                   *      *      -     *
luks                   *      -      *     -
hpfs                   *      *      -     -
romfs                  *      *      -     -
squashfs               *      -      -     -
minix                  *      -      -     *
ocfs (1, 2)            *      *      *     *
vxfs                   *      -      -     *
nss (netware)          *      -      *     *
gfs, gfs2              *      *      *     -
oracleasm              *      *      -     -

Raid members are detected to prevent the probing for a filesystem
-----------------------------------------------------------------
linux raid (md)        *      *      *     *
LVM 1                  *      -      -     -
LVM 2                  *      -      -     *
ddf                    *      -      *     *
highpoint              *      -      -     -
isw_raid               *      -      -     -
lsi_raid               *      -      -     -
nvidia_raid            *      -      -     -
promise_raid           *      -      -     -
silicon_raid           *      -      -     -
via_raid               *      -      -     -
jmicron                *      -      -     -
adaptec                *      -      -     -