Fix some errors and warnings with newer gcc compilers

Hi and thank you for providing this very helpful collection of Matlab wrappers. I'm using the ANN part and I'm quite satisfied with it.

When I tried setting it up, I ran into a few problems that I believe are related to me using a newer version of gcc (4.7.2).

There were errors complaining about undefined functions "exit()" and "strcmp()", which I got rid of by including `<cstdlib>` and `<cstring>`.

Another problem was the usage of `char` instead of `const char` in some places, which is deprecated. Replacing it didn't change the semantics of the code, so I did that too. 

Now the code compiles fine without errors or warnings in Linux using gcc 4.7.2 and Matlab R2012a. Perhaps you want to see if these changes affect the workings of the code on your system and merge them if everything is fine.