keyboard() 'exit' function broken

[John W. Eaton]

On 29-May-2009, Rik wrote:

| The keyboard function for debugging stops normal execution and drops the
| user back to the Octave prompt where they can inspect variables, perform
| calculations to verify intermediate results, etc.  To resume execution
| the user types 'exit' or 'quit'. 
| 
| Unfortunately in the latest tip typing 'exit' doesn't resume execution
| but drops the user completely out of Octave and back to the shell.
| 
| Demonstration code:
| 
| function myfunc
| set_a_variable_for_inspection = 1;
| keyboard;
| end
| 
| Then type 'myfunc' at the prompt which will stop at line 3 and present
| the 'debug>' prompt.  Typing 'exit' will drop the user to the shell.

To continue from the debug or keyboard prompt, type dbcont.  If the
documentation says otherwise, it should be fixed.  FWIW, I think that
this is also the way Matlab works.

jwe