Refactor to use Errno for error reporting

Case 114361: Refactor Filesys::POSIX to use Errno-based error messages for
error reporting, to ensure error messages are appropriately localized by the
system's C library in the vast majority of cases

Changes:

    * Implement Filesys::POSIX::Error with throw() function to simplify
      throwing of errors by number; sets $! to a specified value, and
      throws a stringified $! with Carp::confess()

    * Implement Test::Filesys::POSIX::Error with throws_errno_ok() to
      simplify refactor of unit tests to enforce new interface contract

    * Change a few errors thrown to an errno.h value which better matches
      the behavior of a real Unix environment

    * Update POD to reflect exceptions thrown by their errno.h macro name

    * Update copyright on all files to 2014
Merge branch 'case114361' of git://deathstar.dev.cpanel.net/~erin/filesys-posix/erins-filesys-posix
Add missing strictures to Test::Filesys::POSIX::Error