builder: Move is_block_device function into common utilities.

This is just code motion.
(cherry picked from commit 81b4e5d5cd68f65aa950251e22332b3fa477fecb)
sparsify: Prevent overwriting block or char output devices (RHBZ#1056290).

virt-sparsify doesn't work if the output is a block device, and cannot
possibly work if the output is a char device.  Currently if you try
this it actually overwrites (deletes) the output device which is not
exactly desirable.  Therefore throw an error and exit.
(cherry picked from commit 13bca32e4ec9213e69ea55e837dea846719fb67e)
RHEL 6: Emphasize libguestfs-winsupport package (RHBZ#627468).

This RHEL 6.1-only patch changes the error messages when the
inspection code cannot find an operating system inside the guest
image.  For a Windows guest this may happen because the user has not
installed the separate 'libguestfs-winsupport' package.  Therefore we
emphasize that the user may need to install this package.

Notes:

(1) In RHEL 6.1 there are two pieces of inspection code, the old Perl
code (deprecated upstream) and the new C core inspection API.
Therefore this patch has to touch two places with essentially the same
change.

(2) This patch doesn't try to be clever and detect if it was a Windows
guest.  This should reduce the chance of failure.

Output from (Perl) virt-inspector now looks like this:

 $ virt-inspector disk.img
 No operating system could be detected inside this disk image.

 This may be because the file is not a disk image, or is not a virtual machine
 image, or because the OS type is not understood by virt-inspector.

 If you feel this is an error, please file a bug report including as much
 information about the disk image as possible.

 RHEL 6 notice
 -------------
 libguestfs will return this error for Microsoft Windows guests if the
 separate 'libguestfs-winsupport' package is not installed. If the
 guest is running Microsoft Windows, please try again after installing
 'libguestfs-winsupport'.

Output from guestfish (ie. C core inspection API) now looks like this:

 $ guestfish -i disk.img
 guestfish: no operating system was found on this disk

 RHEL 6 notice
 -------------
 libguestfs will return this error for Microsoft Windows guests if the
 separate 'libguestfs-winsupport' package is not installed. If the
 guest is running Microsoft Windows, please try again after installing
 'libguestfs-winsupport'.
RHEL 6: Require external hex editor set with $HEXEDITOR.

RHEL 6 doesn't have the hexedit program or any suitable replacement.
Require that the user sets $HEXEDITOR to make this command work.
(cherry picked from commit 1ee31426e13446bc5fcce242eb496a01d8a78d8c)
RHEL 6: Directly include String::ShellQuote.

Directly include a snippet from String::ShellQuote so that we
don't need to depend on this external library, which is not
included in RHEL 6.1.

This affects virt-make-fs.
RHEL 6: Modify blkid test so it is successful on RHEL 6-era blkid.
RHEL 6: Remove libguestfs live (RHBZ#798980).

This isn't supported in RHEL 6.
RHEL 6: Exclude iptables from the appliance (RHBZ#858648).
RHEL 6: In mount-local docs, change refs to libguestfs 1.18 -> RHEL 6.4.

We backported the libguestfs 1.18 / mount-local functionality
into the libguestfs 1.16 codebase for RHEL 6.4.
RHEL 6: Ignore /etc/release if /etc/redhat-release exists (RHBZ#872454).

If the user has created /etc/release on a RHEL machine, don't
mis-detect the OS as NetBSD.
RHEL 6: Modify ruby Rakefile.in to work with older Ruby.
RHEL 6: Remove check for qemu >= 1.
RHEL 6: Revert "Use pkg-config for Python"

Python in RHEL 6 does not contain the required pkg-config files.

This reverts commit e5f0dfb6e3425e8dbaa405847ae98a8dcc421da7.
RHEL 6: tests/regressions/rhbz895904.sh: Use `` instead of $().

Apparently bash in RHEL 6 cannot handle this unusual
multi-line use of $(...), but `` works fine.
RHEL 6: Add back some state test commands to guestfish (RHBZ#971664).

In RHEL 6, re-add the following commands to ensure there is no
regression between RHEL 6.4 and RHEL 6.5:

  get-state            get the current state
  is-busy              is busy processing a command
  is-launching         is launching subprocess
  is-ready             is ready to accept commands

(As a side-effect this also adds 'wait-ready' which is a no-op).

These commands have been removed upstream and will be removed
permanently in RHEL 7.  The reason is that these commands do not do
anything useful.
RHEL 6: Pipe 'yes' into ntfsresize (RHBZ#971326).

This works around a problem in ntfsresize on RHEL 6.  See:
https://bugzilla.redhat.com/show_bug.cgi?id=971326#c4
RHEL 6: Remove 9p APIs from RHEL (RHBZ#997884).

(cherry picked from commit 5f7b0f81793f38191634f4460b1c18b97990db44)
RHEL 6: disable fstrim API (RHBZ#982979).

The combination of qemu, kernel & virtio-scsi in RHEL 6 is too old to
make fstrim work properly.
Thus, make the 'fstrim' feature always unavailable, and hide the
'fstrim' command from the documentation.