Shadow calculation methods in Camera
alter lights in ModelBody::Render when in shadow
draw shadows on TerrainBodies in shaders
calculate proportion of disc occluded during eclipse
incorporate SpaceStation atmosphere lighting in ModelBody
adjust ambient/direct lighting calculations to handle high model positions
move ModelBody lighting into new methods, and make them optional in RenderModel
use spacestation's lighting for adjacent city
support multiple shadows on a geosphere
clamp floats with floats
#define PI
Merge branch 'eclipse' of git://github.com/zugz/pioneer into eclipse
Made geosphere_terrain.vert match the Camera.cpp implementation of discCovered.
Got Camera.cpp to compile under VS2012
Added a define to control using the more or less accurate maths function for shadowing.
Of note: the less accurate doesn't flicker.
Merge branch 'eclipse' of https://github.com/fluffyfreak/pioneer into eclipse

Conflicts:
	data/shaders/gl2/geosphere_terrain.vert
	src/Camera.cpp
fix division by zero in discCovered
Merge branch 'master' into eclipse

Conflicts:
	src/SpaceStation.h
improve sky shader handling of shadows - smoother and cheaper
Merge pull request #1353 from zugz/eclipse

planets cast shadows