Topography/XShape: normalize ShapePoints

Fixes potential overflow errors.
TopographyFileRenderer: move projection code to Screen/OpenGL/Geo.cpp

To be reused by the airspace renderer.
NearestAirspace: use nullptr instead of NULL
NearestAirspace: include cleanup
AirspaceIntersectSort: include cleanup
RoutePolars: include cleanup
AbstractReach: remove obsolete (empty) header
RouteLink: include cleanup