Pressure and Humidity now a factor in body temperature and frostbite

With the new weather system, pressure and humidity can now be a factor in body temperature.

The formula used is : http://en.wikipedia.org/wiki/Wind_chill#Australian_Apparent_Temperature

Wind power is a simple formula, but seems to work. 

Clothing resist wind based on coverage and material. Wool is bad, Cotton isn't good, leather / plastic / bone / chitin / nomex is great, the rest (metal, wood, etc) is almost perfect. Bodywetness is now used instead of morale wetness for warmth calculations.

Being inside or underground stops wind and affects humidity.

Being in/under water stops wind, and the new "water temperature" is used instead of air temperature. It is 20C for summer, 10C for fall/spring, and 3C for winter. Totally made up.

The UI is lacking space! Wind speed is described, so is relative humidity. It
s the same color as temperature. However, the @ menu and the + menu now show body temperature on a scale of -100 to 100 instead of warmth.

Frostbite has been refactored and should reflect reality accurately. If anything, the armor buffs against frostbite may need tweaking. There is also a new "recovering frostbite" disease to make sure the player suffers pain due to regaining feeling in iced tissues. Being wet reduces temps by up to 20C for frostbite calculations.

Things that can be improved : UI could be made more space efficient maybe; describing wind and humidity takes up a lot of room. Also, the @ and + menus show current temperature in -100 to 100, but show convergeant temperature (what you will be at given enough time) in color. So if you step out of an ice lab into the hottest day of the year, it might read (-70) in red. I need to find a way to either inform the play, or do this better.

Things missing : Wind has no direction: a wind map is needed for that and beyond my abilities at the moment.
*Seems* like a bug:

This is the overmap terrain *name*, it's later passed as parameter `omtername` to `get_local_windchill`.

There it is compared to what looks like terrain *ids*.
- The terrain name can be translated and the comparison with the terrain id will (most likely) always fail in other languages.
- There is no terrain named "forest_thick", "hive" or "forest_water". Those checks will fail even with the default language.

I suggest using `otermap[cur_om_ter].id` and renaming the parameter and variable to something like `omterid` to reflect its actual content.

The same code is apparently repeated (with the same bug) in `player::update_bodytemp()` in player.cpp.

Also: someone should remove the now useless `game::weather_log` member.