109.47.00

- Added new syntax `<:test_result<>>`, which is similar to `<:test_eq<>>`.

  `test_result` is meant for the common case of comparing some hardcoded
  expected value against one returned by some code you're testing.  In
  this case you can now write, for example:

  ```ocaml
  <:test_result<int>> 3 ~expected:4
  ```

  which behaves exactly the same way as:

  ```ocaml
  <:test_eq<int>> 3 4
  ```

  except that the error message is something like:

  ```
  ("got unexpected result"
    ((got 3) (expected 4)
       (Loc "File \"z.ml\", line 44, characters 25-25")))
  ```

  rather than:

  ```
  ("comparison failed"
    (3 vs 4
      (Loc "File \"z.ml\", line 44, characters 25-25")))
  ```

  The additional labels on the values help identify the problem earlier.