bug#9571: 24.0.50; user option to turn off bidi, please

[Drew Adams]

Dunno if this is still the latest word, but in the emacs-devel thread
"`C-b' is backward-char, `left' is left-char - why?", I was told that
the way for a user to turn off bidi is to set `bidi-display-reordering'
to nil.  Since it is buffer-local, that presumably means putting this
in .emacs if you want to turn it off everywhere:
 
 (setq-default bidi-display-reordering nil)
 
1. That's not very user-friendly.  We should have a user option that
does this, i.e., gives users an easy way to disable this feature if they
don't want to use it.
 
2. I see nothing in the Emacs doc that tells users clearly that if they
want to turn off bidi editing then they should set the default value of
this internal variable to nil.  Users should be told this.
 
The only thing said in the Emacs manual about this variable is this:
 
"The buffer-local variable `bidi-display-reordering' controls whether
text in the buffer is reordered for display.  If its value is
non-`nil', Emacs reorders characters that have right-to-left
directionality when they are displayed.  The default value is `t'."
 
That tells users who are inclined to study it how it works, but we
should be telling all users clearly how they can easily turn it off
everywhere, if they want to.

FWIW, I turn it off because both (a) it slows down Emacs (no, I don't
have a test case and I won't be coming up with one) and (b) I have no
need for bidi editing, at least for now.  If you don't believe (a), then
at least accept (b): I don't _want_ to use it.
 
In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2011-09-19 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.5) --no-opt'