Fix CPANTS test failures

Case 116001: Fix CPANTS test failures with the following changes:

    * Modify Filesys::POSIX::Userland::Tar's $fs->tar() method option
      'ignore_missing' to test $! for ENOENT rather than checking $@,
      which can get localized to something other than what we used to
      expect

    * Modify Filesys::POSIX::Userland::Tar's $fs->tar() to use a blocking
      factor of 20 * 512 bytes; pad end of stream to prevent failure
      untarring on BSD tar

    * Modify t/rename.t to be slightly less anal about expected output
      from tar, to accommodate for slight differences in formatted
      output between GNU tar and BSD tar

    * Modify t/tar-missing.t to use Test::Filesys::POSIX::Error function
      throws_errno_ok()

    * Modify Test::Filesys::POSIX::Error to use Try::Tiny, rather than
      plain block eval(), which causes issues with Perl <=5.12

    * Modify Test::Filesys::POSIX::Error to build a default number=>name
      cache populated with number=>number, in case of an incompatible
      Errno module
Merge branch 'case116001' of git://deathstar.dev.cpanel.net/~erin/filesys-posix/erins-filesys-posix