On the revision:

- Make the .map and .def files prerequisites of the libs type target and only
  on the respective OSes. Also try to generate them on the fly.

- Normalize C comments in the tests source code replacing:

  /*
   * ...
   */

  with

  /* ...
   */

On the release:

- Use legal{} target type for legal documentation (LICENSE, AUTHORS, etc).

  Note that this requires bumping build2 version requirement to 0.13.0.