packet-cfm.c: Update some comments; Add editor modelines.

- Indicate that ITU-T G.8013/Y.1731 (11/2013) is the latest spec
  (and that the cfm dissector has not been updated to reflect same).
- Remove a comment about a "discrepancy in the recommendation
  ITU-T Y.1731". The discrepancy has been corrected in the latest
  spec.

Change-Id: I5a5f873d2a0a5fdee3aef1688403bb317a155cdf
Reviewed-on: https://code.wireshark.org/review/4081
Reviewed-by: Bill Meier <wmeier@newsguy.com>