obsoleting the annotate level 2 interface

[Andrew Cagney]

> GDB seems to support two different ways of doing detailed annotations
> of its output for consumption by other programs: MI and 'set annotate
> 2'.  I don't think annotation level 2 has many active users, if any at
> all.  It pervades GDB's code.  Would it make sense to put 'set
> annotate 2' on the path to obsolescence?

Hmm, yes!  Dead code elimination is always good.
Removing the annotate stuff was always part of MI's long term agenda.

> Some background: the 'set annotate' command sets the
> 'annotation_level' variable.  There are only three distinguished
> values for this variable:

Can you perhaps do a little more research into the history of this 
feature?   For instance, was this initially part of some now abandoned 
project, or was this just `a good idea at the time'?  What of the other 
potential clients (DDD, ...)?  This helps strengthen the non-technical 
rationale for this user interface change.

As for implementing this, the first step is pretty easy, just tweak 
"main.c" to print a warning when level 2 is selected.  (Like the 
`deprecate mechanism we've got for commands'.)

> Personally, I'd like to see Emacs switch from annotation level 1 to
> MI, too; then we could get rid of annotation altogether.  But I think
> it makes sense to tackle level 2 first, since I don't think it has
> many users (if any).

Yes.  RMS has previously inidicated his liking of the idea of having 
EMACS use MI.  The lack of a console was identified as a technical 
barrier to that change :-/

Andrew