Drop dependency from Win32

On v0.008 dzil inserted a dependency from Win32, but this made the
module not build on any platform other than Win32.

I'm dropping the dependency altogether because on Windows it's
guaranteed to be present.
Improve documentation

Signed-off-by: Gustavo L. de M. Chaves <gnustavo@cpan.org>
v0.009

  [Fixes]
  - Drop Win32 dependency which was preventing the build on any other
  platform.