112.01.00

- Removed vestigial code supporting OCaml 4.00.
- Added `Command` support for flags that are passed one or more times.

  Added `Command.Spec.one_or_more` and
  `Command.Spec.non_empty_sequence` to deal with the cases where you
  expect a flag or anonymous argument (respectively) to be passed one
  or (optionally) more times.  This is common enough and distinct from
  the case where you want the argument passed zero or more times that
  it seems like we should canonize it in the library.
- In `Lock_file`, made stale lock detection more robust.

  Made `Lock_file.create foo` succeed if `foo` is absent and
  `foo.nfs_lock` file is present and stale.  Previously, it would
  fail.
- Removed `Syslog.syslog`'s `add_stderr` argument; use the `PERROR`
  option instead.
- Fixed `unix_stubs.c` compilation on NetBSD

  Closes #45
- Added `Filename` operators `/^` and `/@`, and `of_parts`, like the
  same functions for Catalog paths.
- Changed `Iobuf` functions that advance the iobuf to not also return
  a redundant number of bytes processed.

  This avoids a small allocation (in the case of the `int option`
  functions) and normalizes the result (so the same information isn't
  returned two ways).  Actually, it doesn't yet avoid the allocation in
  the implementation, as the corresponding `Bigstring` functions must
  still return the number of bytes processed, and currently do so as an
  option.  We hope to eventually change that.

  In the future I expect we will change `unit` to some `error` variant
  to also avoid the exception construction for `EWOULDBLOCK/EAGAIN`.  We
  can even make Unix syscalls `noalloc` if we're careful.
- In `Unix` module, added unit tests for `Cidr.does_match`.