This adds functions to register the command line arguments to use the API in the same way as is done for tethereal.
Later it may be extended to also register the GUI/Menu entry point to ethereal using this api but that iwll be later since the changes required to menu.c are not as intrusive as the main.c command line parsing ones were.
Some of the latest changes (before this checkin) has made ethereal to produce lots of GTK errors when starting up the extension windows.
They were there before this checking but will be investigated.
svn path=/trunk/; revision=6566
