Minor compatibility release

• Don't break the build if Block.connect has optional arguments

Optimise out an unnecessary flush

• Remove one necessary source of flush calls
• CLI: add mapped command to list the mapped regions of a file

Extra paranoid metadata consistency release

• For buffered block devices, call flush to guarantee metadata correctness
• In lazy_refcounts mode (the default), do not compute any refcounts
• CLI: the repair command should recompute refcounts

No camlp4 release

• Depend on ppx, require OCaml 4.02+

Support qcow version 3

• Use qcow version 3 by default, setting lazy_refcount=on
• Unit tests now verify that qemu-img check is happy and that qemu-nbd sees the same data we wrote

Initial release

• initial V1_LWT.BLOCK support
• caches metadata for performance
• CLI tool for manipulating images
• supports the seek_mapped seek_unmapped interface for iterating over
  sparse regions