* a workaround for broken YAML::Syck

  YAML::Syck 1.12 (which is in Debian squeeze) seems to create an
  undef instead of an integer value in the last PathIndex entry. This
  seems to be fixed in YAML::Syck 1.22 (which in in FreeBSD 9).

  The workaround is to force an integer here using "0+".