Editcap: Don't treat plain -F and -T as errors.
The editcap man page says that you can pass in -F and -T without
arguments in order to get a list of valid capture and encapsulation
types. Instead of treating these as errors just print the information to
stdout and return 0.
Adjust the docbook _tools_help targets accordingly.
Change-Id: I590cbd59059dd8965299bef4434f522eff8a4e2c
Reviewed-on: https://code.wireshark.org/review/23741
Reviewed-by: Gerald Combs <gerald@wireshark.org>
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>