Fixing a corrupted .pn2 file, causing Greenland ice to extinct

Greenland ice is back, Congrats!!!

REVIEW: 121522
introduce MarbleView
introduce MarbleGLView
introcude GlLayerInterface
clear depth buffer between layer rendering
TextureLayer
PlacemarkLayer
introduce triangulation algorithm for polygons

* taken from http://www.crystalspace3d.org/svnroot/crystal/CS/trunk/{include/csgeom/triangulate.h, libs/csgeom/triangulate.cpp}.
GeometryLayer
introduce GeoGraphicsScene::GlTile and use glDrawElements
adapt PlacemarkLayout
use shaders
GLRenderer
cosmetics
attributes--
split matrices in texture vertex shader
wip projection in shaders