Small enhancements.
The CDLOD prototype is more or less working.
Better morphing.
Implemented the frustum culling (+8% fps on average).
Now only 4 render calls per frame for the terrain.
Now CDLOD can work even if VertexAttribDivisor is not available, but will run about 20% slower.
Looks good, but it aint too fast...

Also I should really get a better heightmap!
Small changes.
The min-max selection, and the camera culling now works fine.

Note: never trust your own code.
Forgot to add some changes in the last commit.
CDLOD now seems to work way better than geomipmapping. But the heightmap still sux.
Code cleanup.
New heightmap, disables shadows, srgb fix.
Small update.
Merge branch 'CDLOD'

Conflicts:
	shaders/terrain.frag
	src/engine/camera.h
	src/main.cc