Cholesky updating

[John W. Eaton]

On  5-Mar-2008, Jaroslav Hajek wrote:

| I've tried to address all the issues pointed out by John. A changeset
| is attached.
| 
| Consider also applying the subsequent changeset - it changes the QR
| row/col insert/delete methods to use 0-based indexing (for consistency
| with the rest of liboctave, though this means slightly more fiddling
| with indices).

I applied both of these changes.  I noticed the 1-based indexing but
forgot to mention it in my earlier message.  Thanks for catching it.

jwe