bug#14467: 24.3.50; semantic-symref fails to fall back to grep when cscope.out is removed

[Jambunathan K]

1. Setup cscope as symref tool for ~/src/emacs/trunk/src.  

2. C-c , g  intervals_equal

   Make sure that cedet-cscope.el is the symref tool used for producing
   above results.

   For basic help with (1) and (2) steps see
   http://debbugs.gnu.org/cgi/bugreport.cgi?bug=14455

3. M-x delete-file RET ~/src/emacs/trunk/src/cscope.files RET
   M-x delete-file RET ~/src/emacs/trunk/src/cscope.out RET

4. C-c , g  intervals_equal

   Note that the search fails with output

      ,----
      | semantic-symref-produce-list-on-results: No references found
      `----

5. Restart Emacs

6. While browsing Emacs C files, do

   C-c , g intervals_equal

   See that the results are produced with grep as the backend.


Expected behaviour: Do away with step (5).  

For example, cscope.out may have been accidentally removed because of
(say) a version control clean operation (like git clean -d -f).  Symref
should do it's try hard to give results and not continue to expect that
the eariler backend is still functional.


In GNU Emacs 24.3.50.3 (i686-pc-linux-gnu, GTK+ Version 2.20.1)
 of 2013-05-25 on debian-6.05
Bzr revision: 112729 monnier@iro.umontreal.ca-20130525030804-6onx9rhvib7pv3fc
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
Important settings:
  value of $LANG: en_IN
  locale-coding-system: iso-latin-1-unix
  default enable-multibyte-characters: t