Core 111.08.00

## New package: bignum

A Core-flavoured wrapper around zarith's arbitrary-precision rationals.

## async_extra

- Added `Log.Message.add_tags`, which extends a message with a list of
  key-value pairs.

        val add_tags : t -> (string * string) list -> t

## async_kernel

- Changed low-level error messages to use `Sexp.to_string_hum` rather
  than `to_string_mach`.

## async_ssl

- Improved the propagation of SSL errors to the caller.

## async_unix

- Added `Sys.when_file_changes : string -> Time.t Pipe.Reader.t`.
- Added `Time.now ()` to some error messages.

## core

- Improved `Command` to print a good error message if command-line
  parsing raises.

	`Command`'s `Exn.handle_uncaught` now protects the phase of parsing
	command-line arguments in addition to protecting the phase of
	running the `main` function as it did already.

## core_kernel

- Added `Hashtbl.for_all` and `for_alli`.
- Added `Float.to_padded_compact_string` for converting a floating point
  number to a lossy, compact, human-readable representation.

    E.g., `1_000_001.00` becomes `"1m "`.

- Tweaked the form of the definition of `Blang.Stable.V1`.

    Removed a `type t_` that is not necessary now that we can use `nonrec`
    without triggering spurious warnings.

## enumerate

- Restricted the signature of the `all` value generated by
  `with enumerate`.

    Now, in:

        type t = [ `Foo | ... ] with enumerate

    the type of `all` will be `t list`, instead of `[> t] list`.

    When taking unions of polymorphic variant types, inserted the
    appropriate coercions.

    Fixes #1.

## jenga

- Fix a hang.

    Jenga could reach a state with a non-zero todo-count, but have no
    jobs actually running, and then hang in this state forever. The hang
    would be evident from a progress line with not all targets built and
    with `j=0+0` such as:

        todo: 17 (100406 / 100423) j=0+0 con=149956 act=3303, finish at: 16:20

## ocaml_plugin

- Use `ocamldep` to generate the dependencies of an `.ml` file, if
  requested.

	Added a function to find the dependencies of a module, but did not
	change the existing behavior and interface of the library if one
	does not choose to use this functionality.

## pa_test

- Made it possible to use `<:test_eq< >>` and friends in `Core_kernel`.

    Removed the dependency of the code generated by `pa_test` on
    `Core_kernel`, so `pa_test` can be used there.

## re2

- Upgraded to upstream library version 20140304. 

    Added options `Dot_nl` and `Never_capture`.