Completely remove "old style" dissector support.

Completely remove "old style" dissector support.

The typedef for the "old style" has been removed as well as any old vs new style checks.

The release notes have been updated to reflect the API change, even though the search/replace of the "new style" function names hasn't happen yet.  But it will be coming shortly...

Change-Id: I6d1eeb51d30e3b2b27f0eafd85fe0ddc0ca25b14
Reviewed-on: https://code.wireshark.org/review/12153
Petri-Dish: Anders Broman <a.broman58@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>