111.11.00

- Change some `Bigstring` functions to retry on `EINTR` rather than
  raise.

  The following functions (and their unsafe versions) were affected:

  * `read`
  * `really_read`
  * `really_recv`
  * `really_write`
  * `really_send_no_sigpipe`

  Some other `Bigstring` functions, like `input` and `output`, already
  retried on `EINTR`, so this change has precedent.

  All of the affected stubs raise `Bigstring.IOError` on failure,
  rather than `Unix_error`, which means the normal method for retrying
  on `EINTR` doesn't work.  In particular `Async.Reader` didn't retry
  them, even though it was supposed to.

  Additionally, the documentation for the following functions was
  corrected to say that they raise =Unix_error= rather than =IOError=:

  * `pread_assume_fd_is_nonblocking`
  * `pwrite_assume_fd_is_nonblocking`
- Eliminated global binary-to-decimal tables computed at startup for
  converting `Date` and `Of_day` to string.

  Used an efficient implementation of division by 10, rather than the
  `sprintf` tables in `time_internal.ml`.  This result in much less
  allocation at startup and it is a bit faster:

  * before:

  | Name           | Time/Run | mWd/Run | Percentage |
  |----------------|----------|---------|------------|
  | Date.to_string |  69.39ns |   3.00w |    100.00% |

  - after:

  | Name           | Time/Run | mWd/Run | Percentage |
  |----------------|----------|---------|------------|
  | Date.to_string |  53.38ns |   3.00w |    100.00% |
- Fixed `Time.Zone` tests so that they are deterministic.
- Added `Iobuf.to_string_hum`, which produces a readable, multi-line
  representation of an iobuf, intended for debugging.
- Fixed brittle unit tests of `Command`.