#94 Update the GSL port to 2.5

[Analabha Roy]

Hi,

It would be nice if the native windows port of the GNU Scientific Library were updated to the latest version (2.5). The version currently hosted (1.8) @ http://gnuwin32.sourceforge.net/packages/gsl.htm is rather old and deprecated. I'm teaching Scientific Computing to Masters students and to undergraduate teachers, and need to deploy GSL to the windows machines of our department and those in our affiliated colleges.

I managed to cross-compile gsl-2.5 for 32 and 64 bit for windows 10 in my ubuntu laptop.
Details are @ https://sites.google.com/phys.buruniv.ac.in/programming-workshop-cbcs/setup?authuser=0#h.p_LjLvAWAHptz9
It would be better if it were built and hosted by the gnuwin32 project, though.

Thanks and Regards,
Analabha Roy