[Libguestfs] [PATCH v3 00/10] Add discard support.

This set of patches: - Adds new APIs to support discard in libguestfs. - Adds discard support to virt-format. - Adds discard support to virt-sysprep. - Implements virt-sparsify --in-place. This is now working, after fixing the rather stupid bug in fstrim. I've pushed the ones which were ACKed previously + the fstrim fix. Rich.