Allow for alternative Blorb file at command line for dumb and curses.

Allow for alternative Blorb file at command line for dumb and curses.

Doing this for the SDL interface is proving troublesome because it's not
very clear where stuff is being set and where not.  After the audio
overhaul release, I want to overhaul the SDL interface code to make it
as closely resemble as feasible that of the curses interface.