1.8.6

version 1.8.6

Changes since 1.8.5:

• update_mmap and update_mmap_rayon (and by extension b3sum) now
  use seek rather than metadata to get the length of a file/mapping,
  and they tolerate mmap failures. That means b3sum will now memory
  map e.g. Linux block devices, which support mapping despite reporting
  length 0 in metadata. Hashing NUL files on Windows also works now,
  where previously it was an error unless you used --no-mmap or <.
  This change was originally proposed by @nabijaczleweli.