[Libguestfs] [PATCH nbdkit v2 0/4] Support MBR logical partitions.

This is a revised version of the two series previously posted here: https://www.redhat.com/archives/libguestfs/2019-January/msg00137.html https://www.redhat.com/archives/libguestfs/2019-January/msg00139.html There have been many smaller changes but the highlights are: - Using SECTOR_SIZE instead of hard-coding 512 everywhere. - Additional safety checks that the EBR chain doesn't jump outside the disk. - The better test now writes different random data into each partition rather than the same string. - I pushed the pure refactoring changes. Rich.