[Libguestfs] Various fixes from building libguestfs for Debian

[Hilko Bengen]

Here are some of the patches that I have maintained in the patch queue
of my packages that I maintain within the Debian distribution
(http://packages.qa.debian.org/libg/libguestfs.html). All of them
address FTBFS (fail to build from source) errors that happened with
the particular configuration that is used for building the Debian
package.

Cheers,
-Hilko