Changed windchill model [CR]

I've decided to change the windchill model based on this forum post : http://smf.cataclysmdda.com/index.php?topic=8002.msg184741#msg184741

There is a bug in my code that I am blind to : windchill always turns "1" ??? I don't understand why. Hoping someone with C++ experience could point it out.

This PR also adds a debug item, the pocket meteorologist, which simply messages the player the absolute temp, pressure and humidity. Once the windchill=1 bug is fixed, I can remove the item if necessary.
I get windchill of -1 up to 8 (temperature=23, humidity=86, windpower=0 or similar) during the first day.

The cast to float here is most likely not what you want, at least not needed (the involved values are already double).
Also the cast to int when return the value is not needed. The return value is per function declaration an int and is automatically convert to.