Terrain: create 4x4 terrain chunks per ESM::Cell to improve performance

Improves performance because the number of splatting layers per chunk is reduced, and finer grained frustum culling can be done.

components/terrain/buffercache.cpp

@@ -1,6 +1,7 @@
 #include "buffercache.hpp"
 
 #include <cassert>
+#include <iostream>
 
 #include <osg/PrimitiveSet>
 
@@ -208,6 +209,8 @@ namespace Terrain
     {
         unsigned int verts = mNumVerts;
 
+        std::cout << "getting index buffer for " << verts << std::endl;
+
         if (mIndexBufferMap.find(flags) != mIndexBufferMap.end())
         {
             return mIndexBufferMap[flags];