Type of weather changed from string to enum.
Simpler statistical calculation of next weather; minus before parens.
WeatherResult added as member variable.
Removal of duplicit exterior checking and unneded string copiing.
Merge branch 'master' of https://github.com/zinnschlag/openmw into weather
Static for nextWeather()
Correction of sigsegv.
Revert "Type of weather changed from string to enum."

This reverts commit 04d90b4c47e140cec53750d523378d2cf9938387.

Conflicts:
	apps/openmw/mwworld/weather.cpp
	apps/openmw/mwworld/weather.hpp
killed a stray srand