search for: set_progress_callback

This is an updated and extended version of the original patch: https://www.redhat.com/archives/libguestfs/2010-August/msg00163.html This adds OCaml and Perl bindings (both tested), support for progress bars in virt-resize, and adds progress notifications to a number of the simpler commands. Still to do is to add progress messages to more commands. There are still a few commands which would be