bug#14433: 24.3; comint-history-isearch-backward-regexp not working properly in inferior octave

[Leo Liu]

1. emacs -q
2. M-x run-octave
3. M-r
4. typing a few chars

You should observe a gigantic output (for example 40k lines) in the
buffer:

,----[ sample output ]
| ................................
| Please contribute if you find this software useful.
| For more information, visit http://www.octave.org/get-involved.html
| 
| Read http://www.octave.org/bugs.html to learn how to submit bug reports.
| 
| For information about changes from previous versions, type `news'.
| 
| octave> ave> GNU Octave, version 3.6.4
| Copyright (C) 2013 John W. Eaton and others.
| This is free software; see the source code for copying conditions.
| There is ABSOLUTELY NO WARRANTY; not even for MERCHANTABILITY or
| FITNESS FOR A PARTICULAR PURPOSE.  For details, type `warranty'.
| 
| Octave was configured for "x86_64-apple-darwin12.3.0".
| 
| Additional information about Octave is available at http://www.octave.org.
| 
| Please contribute if you find this software useful.
| For more information, visit http://www.octave.org/get-involved.html
| 
| Read http://www.octave.org/bugs.html to learn how to submit bug reports.
| 
| For information about changes from previous versions, type `news'.
| 
| octave> ave> 
`----

This is due to the first prompt not a proper comint prompt. I'll install
a fix soonish.

Leo