This makes it easier to create the matching array of type names in
bidi_gettype.c, and eliminates the need for an assertion to check the
array matched the enum. And I'm about to need to add more types, so
let's start by making that trivially easy.
That's what I've usually been doing with any main()s I find under
ifdef; there's no reason this should be an exception. If we're keeping
it in the code at all, we should ensure it carries on compiling.
I've also created a new header file bidi.h, containing pieces of the
bidi definitions shared between bidi.c and the new source file.
This contains terminal.c, bidi.c (formerly minibidi.c), and
terminal.h. I'm about to make a couple more bidi-related source files,
so it seems worth starting by making a place to put them that won't be
cluttering up the top level.
