[libvirt] [PATCH 00/28] Convert more of configure.ac to use helper macros

This is a follow-on series from https://www.redhat.com/archives/libvir-list/2013-January/msg00647.html It converts all the remaining easy library/package checks to use the new helper macros. What's let are some tricky cases where we first check via pkg-config and then fallback to a manual check, or cases where we use a custom pkg-config like program