Convert from xyz to lle as the main roam coordinates

Convert from xyz to lle as the main roam coordinates

This keeps splits along latitude lines instead of along great circles.
It is a little less accurate, but makes texture mapping much simpler, at
least with Mercator projections.

If we ever manage to get lle->xyz conversions done in an OpenGL shader,
this should make the transition a little easier as well.

     Old Way           New Way
    .-''/'''-.        .-''/'''-.
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  /''  |     ''\    /    |       \
  *..__*_____..*    *..__*_____..*
  \    |       /    \    |       /
   \   \      /      \   \      /
    '-..\...-'        '-..\...-'