Improve checkfiltername.pl for pre-commit script.

1. Bugfix grep statement checking if file is "autogenerated"
2. Add to the list of "whitelist" duplicates.  Many more were found after #1 was changed.

Change-Id: Idea764c0c8b5fa4f30c9acaab9ba10340834d4f5
Reviewed-on: https://code.wireshark.org/review/5547
Petri-Dish: Evan Huus <eapache@gmail.com>
Reviewed-by: Evan Huus <eapache@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>