labelling further-out objects
wider vertical field of view
I no longer have _header.glsl. Those didn't need to be separate
Extended rear clipping plane logic, color-coding

- Far clipping plane pushed way back; mountains were being clipped that
  shouldn't have been

- Terrain coloring now uses a different far clipping plane, to boost the dynamic
  range of the color

- Reversed coloring direction: near terrain is bright red; far terrain is dark
  red
remvoed unneeded memory re-allocation