Add the fileformats and I/O suites. Move some more common code to
subprocesstest.py and add a diffOutput method.
Change-Id: I2ec34e46539022bdce78520645fdca6dfc1a8c1a
Reviewed-on: https://code.wireshark.org/review/27183
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Gerald Combs <gerald@wireshark.org>