[Libguestfs] Various fixes from building libguestfs for Debian

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