GTK+: Make sure we package up Wireshark-gtk.pdb.

Make sure we use $(PROGRAM_NAME_GTK) consistently. We still need to add
the Qt UI .pdb to the archive but I'm not in front of a proper Windows
development environment right now.

Change-Id: Ie917f68e3e8349fc7955b3b7e68d446b6fe88235
Reviewed-on: https://code.wireshark.org/review/4096
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Gerald Combs <gerald@wireshark.org>