(PUP-2521) Remove windows-pr

 - Windows::Error no longer exists and the ERROR_FILE_NOT_FOUND
   constant is part of the Puppet codebase now.
 - Catch appropriate error in package specs
 - Remove windows-pr, win32-api and windows-api from gemspec
Merge pull request #2835 from Iristyle/ticket/master/PUP-2521-remove-windows-pr-gem

(PUP-2521) Remove windows-pr gem