patch for loops over multi-dimensional matrices and cell arrays plus documentation thereof

[John W. Eaton]

On 26-Apr-2007, David Bateman wrote:

| There is a minor bug that can be seen with the example
| 
| a = [1,3;2,4]; b = cat(3,a,2*a);
| for i = b
|   i
| end
| 
| which reshapes b like reshape (b, rows(b), prod(size(b)(2:end))) and
| then loops over the columns of the matrix. This is the matlab compatible
| behavior, and what I remember was the behavior we had a few years back.
| The patch also documents this behavior, and adds a couple of tests.

OK, please check in this change.

Thanks,

jwe