[libvirt] [PATCH] allow to set path to xen userspace tools

Hi, attached patch makes the path to the xen userspace tools configurable. Debian keeps this under /usr/lib/xen-default/ instead of /usr/lib/xen/. We don't have the amd64 libs in /usr/lib64/xen either so we can use: ./configure --with-xen-tools=/usr/lib/xen-defaults --with-xen-tools64=/usr/lib/xen-defaults instead of patching src/xen_internals.c directly. Skipping above options gives the current behaviour. I checked that "make check" still passes. O.k. to apply? Cheers, -- Guido