removing old `inverse lines' code

[Miles Bader]

With the changes a while back to only use faces for drawing
inverse-video mode-lines, the `inverse_p' field in `struct glyph_row' is
no longer set anywhere, so it's always zero.

Given that this support seemed redundant anyway, I removed the field,
and went through and simplified all the code that had used it.

I then realized that one wrinkle of not using this field is that
terminals with a `magic cookie' inverse-video implementation (where
switching to/from inverse-video actually takes up a character position)
will no longer show inverse-video mode-lines [though they'll still work
fine otherwise].

I don't really think this is a big deal, since such terminals were
already obsolete 15 years ago, and I doubt very many people use them
anymore (I'd be interested to know if _anyone_ does).  Most other
programs don't support them.

So I decided just to delete all the hair in term.c that is for
magic-cookie standout support as well.  The end result is about 400
lines of code being deleted, with no loss of functionality (since magic
cookie inverse-video stopped working as soon as the mode-line behavior
was changed a while back).

So... what do you think?  Is it worth it to keep this crufty old code
even though it's not used?

Here's the patch:

inverse_p-delete-2.patch
Description: Patch to remove glyph_row inverse_p flag and magic-cookie standout support

-Miles
-- 
o The existentialist, not having a pillow, goes everywhere with the book by
  Sullivan, _I am going to spit on your graves_.