Working version of expmv in Octave

[Chiara Segala]

Dear all,

I'm Chiara Segala, I have proposed myself for GSoC 2016 with the project Exponential Integrators.
Regardless of the project, I wanted to warn you that I have prepared a version of expmv that works in Octave.
I made some changes to the code of N. J. Higham, which gave an error due to the fact that handles to nested functions are not yet supported in Octave. I use also the available code of Marco Caliari normest1.
I conclude with a few minor changes and then I send the file to the patch tracker.

Best regards,
Chiara