[Libguestfs] [PATCH supermin v3] Supermin 5 rewrite.

This is the first really working version of supermin 5. This version can prepare a supermin appliance, and build a full appliance from a supermin appliance. See examples/build-basic-vm.sh for example usage. Read the updated supermin(1) man page for the details. Among the improvements: - Package names are used instead of hostfiles. This should improve robustness, since adding a new file to a package or moving files around won't break the appliance. From the libguestfs point of view this will also allow us to split libguestfs dependencies into subpackges (libguestfs-xfs, libguestfs-ntfs, etc). - It uses the current package database to do dependency resolution, (instead of yum/apt). This is considerably faster. - It only needs to download packages that contain configuration files, which results in much less network bandwidth used. (--use-installed is supported as before to completely eliminate network usage) - --if-newer and --lock options move the locking into supermin (previously it was done in libguestfs). This makes supermin much easier to consume from other programs. - The --if-newer option checks the RPM database instead of iterating over the filesystem, making it much faster (a single stat versus 1000s of stats across the filesystem). - You can create a chroot filesystem from a supermin appliance. Currently missing: - support for Debian / dpkg - support for other distros (that were supported by v4) I intend to add at least Debian support before pushing anything. Some dropped features: - -f cpio is no longer supported. We didn't use this in libguestfs since 2010. It would not be hard to add this back. - --user/--group options. We added these for the benefit of virt-v2v but it's not clear if they are needed. Easy to add back if required. - You can no longer create a supermin from package files. This was never used by callers, as far as I know. - You can no longer exclude packages after depsolving. However you can still exclude files, which is nearly the same thing in practice. Rich.